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Topic: ? has the ONR been up 2?(tech) | Topic page views:
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Alpha-Theta
Superior

ª×µ»ƒ³²² 694 posts, May 2002
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posted 06-07-2002 02:20 PM
This is an enormous list of ONR research contracts that have been granted, all technical in nature and validated and verified by the referrences given. Title: THz-Bandwidth, Deep Submicron, Regrown-Base Transfer-Substrate HBTs
PI: Mark Rodwell THE REGENTS OF THE UNIVERSITY OF CALIFORNIA SANTA BARBARA Department of Electrical and Computer Engineering Address: CHEADLE HALL RM 3227 Santa Barbara, CA 93106 (805) 893-3244 Funding Agency: Office of Naval Research PR Number: 00PR00014-00 Award Number: N000149910041 Current End Date: 30-Sep-2001 Scientific Officer: John Zolper Objective: A low parasitic heterostructure bipolar transistor (LP-HBT) will be scaled down to an emitter width of 0.1 microns to achieve the first THz transistor. Approach: A transfer substrate flip wafer process is being developed for a low parasitic heterojunction bipolar transistor (LP-HBT) whereby the n-type semiconductor under the p-type base contact region is removed to dramatically reduce the base-collector capacitance. The structure will be scaled down to a 0.1 micron emitter width that should produce the first THz transistor. The work will employ an InP collector to improve the breakdown properties over previous devices. Progress: This program seeks to develop very high speed transistors (HBTs) using a transferred-substrate technique. By scaling the devices to very small dimensions, HBTs have been produced with power-gain cutoff frequencies as high as 1080 GHz, 3.5:1 higher than any other HBT and 1.8:1 higher than any other kind of transistor. Efforts to obtain high current-gain cutoff frequencies have resulted in a record 254 GHz ft, and a number of wafers have been processed with the recent goal of obtaining much higher ft. Title: Piezoelectric Doping for GaN Heterojunction Bipolar Transistors PI: Peter Asbeck THE REGENTS OF THE UNIVERSITY OF CALIFORNIA SAN DIEGO 0934 Department of Electrical Engineering Address: 9500 GILMAN DRIVE La Jolla, CA 920930407 (619) 534-6713 Funding Agency: Office of Naval Research PR Number: 00PR00026-00 Award Number: N000149810539 Current End Date: 31-Mar-2001 Scientific Officer: John Zolper Objective: Use strong piezoelectric effect in AlGaN/GaN layers grown in SiC to achieve enhanced hole densities and thereby produce high power heterostructure bipolar transistors in this material system. Approach: Holes densites on the order of 2e18 cm-3 will be generated in the base of a AlGaN/GaN collector-up HBT grown on SiC. This will be accomplished by growing a graded AlGaN layer in the base of the transistor. The hole enhancement will first be studied in diode test structures prior to complete HBT fabrication. Complete collector-up HBTs will be fabricated and characterized at dc and microwave frequencies. Following successful demonstration of the collector-up HBT, novel designs will be implemented to reduce extrinsic emitter injection either by ion implantation or selective area lateral epitaxial overgrowth. Progress: Preliminary designs of the HBT has been developed. Material structures have been specified and are ready for growth at partnering institutions. Simulation studies of the hole concentration expected in the base layer have been carried out based on the piezoelectric effect and the incorporation of Mg acceptors. Stress relaxation in 3 dimensions has been studied in a finite element simulation, to determine if the piezoelectric charge will be significantly modified at the edges of the devices. For the collector-up device, current confinement in the intrinsic emitter was studied. It was found that it is critical to minimize current spreading in the extrinsic emitter region. A novel structure for improvement in base contacts based on piezoelectric doping has been devised, and structures for potential implementation of the concept have been designed. Acceptor-like doping from spontaneous and piezoelectric polarization in AlGaN/GaN HBT structures was theoretically evaluated. Experimental samples to measure this doping (together with that from modulation doping using Mg) were designed. After epitaxial growth at NCSU (Prof. R. Davis), the samples were measured. Results confirm doping contributions of the magnitude expected. Structures with n-type base regions (hot electron transistors) have also been designed and are being fabricated. Title: Materials Physics & Electron Transport Issues in Superconducting Electronics PI: Robert Buhrman CORNELL UNIVERSITY School of Applied & Engineering Physics Address: 120 DAY HALL ITHACA, NY 14853 (607) 255-3732 Funding Agency: Office of Naval Research PR Number: 00PR00092-01 Award Number: N000149710142 Current End Date: 31-Oct-2002 Scientific Officer: Deborah Van Vechten Objective: To provide output from the PI's previous efforts regarding the cause and remedies of inhomogeneous oxygen distribution in YBCO to applications such as high performance HTS filters, high current density (Jc) conductors, and HTS Josephson junctions wherein such inhomogenities may deleteriously impact performance. Improved ability to apply HTS materials to Navy problems should result. Approach: To collaborate with several other groups. Whether the 5-10x improvement following ozone treatment of the Jc of large angle grain boundaries is reproduced in the predominantly small angle case of IBAD textured tape will be tested in conjunction with 3M and Stanford. The impact of the same treatment on microwave surface loss and IP3 will be tested at NIST. Details of the effect of ion beams on the surface of YBCO will be studied to look for both surface passivation coatings and improved uniformity junction tunnel barriers. A small effort will look at normal metal barriers for NbN based junctions in order that we have a self-shunted option for this higher temperature digital material. Progress: Inhomogeneous oxygenation produces variation in the superconducting properties of HTS materials and, if the material is used as a barrier in a Josephson junction structure, to non-reproducible tunneling characteristics. It is thus significant that doping, as with Co in the most common barrier material, produces local stress fields that reduce the oxygen binding energy and lead to inhomogeneous concentrations. As a result only ozone annealing can produce full oxygenation. When done to grain boundary and engineered interface junctions, a Jc independent IcRn product results, a strong virtue. This understanding should assist the development of improved HTS JJ. A modified Blonder-Tinkham-Klapwijk model has been successfully used to directly measure the interface scattering and spin polarization of electrons traversing a clean ferromagnetic-superconductor interface. Title: PLASMA WAVE ELECTRONICS DEVICE UTILIZING TWO-DIMENSIONAL ELECTRON FLUID PI: Michael Shur RENSSELAER POLYTECHNIC INSTITUTE Address: Thornton Hall Charlottesville, VA 22903 (804) 942-4270 Funding Agency: Office of Naval Research PR Number: 00PR00187-00 Award Number: N000149810210 Current End Date: 04-Jan-2001 Scientific Officer: John Zolper Objective: Develop theory and experimentally demonstrate the application of the plasma wave properties of the two dimensional electron gas in high mobility transistors as a high frequency detector. Approach: The non-linear theory will be developed for an arbitary load, for wide bandgap semiconductors, for detectivity, and for the analysis of detector arrays. The experimental work will involve the design, fabrication, and characterization of non-resonant and resonant detectors, and for detector arrays. Progress: Investigations were performed on microwave GaN-based HEMT detectors and, for the first time, terahertz GaAs-based HEMT detectors. Both types of transistors operated at frequencies much higher than their cutoff frequency. The gate voltage dependence is in good agreement with the theory developed under the program. Polarization dependencies were discovered. The measured temperature dependence of the detector responsivity suggests a high viscosity of the electronic fluid. A new theory was developed that predicts the dynamic range of the terahertz HEMT detector.In the past year, we demonstrated experimentally the first terahertz (2.5 THz) detector utilizing an AlGaAs/GaAs High Electron Mobility Transistor (HEMT). The bias dependence of the measured detector responsivity is in agreement with the analytical detector theory. Also, this detector is sensitive to the polarization of the terahertz radiation. We have performed modeling and characterization of 0.25 micron GaN-based HEMTs including the noise characteristics and the electron mobility since high-mobility samples are required for GaN terahertz detector fabrication. Theoretically, we have studied the detector large signal theory and the nonlinear detector theory for an arbitrary load. We have also studied the influence of scattering of carriers on the "shallow water wave instability" of the surface plasma waves in a HEMT. Title: Broadband Microwave Traveling Wave Power Amplifiers PI: Kevin Webb PURDUE RESEARCH FOUNDATION Department of Electrical Engineering Address: Hovde Hall, 3rd Floor West Lafayette, IN 47907 (317) 494-3373 Funding Agency: Office of Naval Research PR Number: 00PR00192-00 Award Number: N000149810371 Current End Date: 30-Sep-1999 Scientific Officer: John Zolper Objective: To design and fabricate high power traveling wave amplifier circuits using AlGaN/GaN transistors developed under the Cornell MURI. The proposal is configured to parallel the MURI in time frame and option structure. Approach: To perform detailed characterization of high power transistors developed under the Cornell MURI and to develop nonlinear models for these devices. These device models will then be used to design high power traveling wave amplifiers. Said amplifiers will be fabricated and tested under this contract. Progress: In collaboration with Prof. Eastman, et al., from Cornell, the PI has designed high efficiency Class A traveling wave and distributed (compact) monolithic GaN HEMT amplifiers that have no drain line dummy termination. These designs used a nonlinear HEMT model derived from measured data. Forthcoming experimental data is expected to support the design concept, which can then be transferred to a Class B push-pull design. Prior to achieving these designs, investigatations will be performed of fundamental issues related to broadband amplifiers and device models, including stability, matched terminations, drain and gate line matching, the basis and accuracy of the HEMT model, and physical implementation strategies. Fabrication of these amplifiers is underway at Cornell. Title: Ultra-Linear Dynamically Programmable Analog to Digital Converter PI: Oleg Mukhanov HYPRES INC Address: 175 CLEARBROOK ROAD ELMSFORD, NY 10523 (914) 592-1190 Funding Agency: Office of Naval Research PR Number: 00PR00211-02 Award Number: N0001499C0089 Current End Date: 30-Dec-2000 Scientific Officer: Deborah Van Vechten Objective: Seek a dynamically programmable analog to digital converter wherein the performance may be programmed from 19 effective bits of resolution with 116 dB spur-free-dynamic-range (SFDR) at 20 MHz sampling speed to 9 effective bits resolution with a 70 dB SFDR at 2 GS/s. Approach: Low transition temperature superconductors, in particular Nb, will be used to fabricate the circuits using Rapid Single Flux Quantum (SFQ) logic. All demonstrations to be done using liquid He cooling. A high-speed single bit quantizer will produce quantized pulses at a rate dependent on the input signal current. The time at which these pulses arrive at the synchronizer is resolved and determines the digital data stream. Both on-chip superconductive decimation and ratio programmable room temperature decimation will be used to vary the sample speed and accuracy of the final samples. The work will increase the number of synchronizer elements and thus timing accuracy within a clock cycle and increase the clock speed of the current design. Perfection of chemical mechanical polishing, improved lithographic resolution of devices, and an increase in the speed of the interface to room temperature circuits is required for success. Progress: A complete 20 GHz ADC design was finished, including a new front-end and a new digital filter. The circuit showed 20 GHz operation of the separate ADC sections after the first design iteration, substantially higher than the previous maximum of 13 GHz. A 25 GHz digital filter design was completed and operated properly in a four-bit implementation in the standard 3-um process. Room temperature interface and decimination filtering components were successfully tested up to 1 GS/s. Operation to 240 GHz was demonstrated in a toggle flip-flop fabricated using SUNY's 1.5-um process. The in-house 1.5-um process has demonstrated high-Jc 100 shunted-JJ arrays and the conversion of digital cell library to this new process has begun. Title: High Speed Analog to Digital Converter with Large Dynamic Range & Programmable PI: Joseph Jensen HRL LABORATORIES LLC Address: 3011 MALIBU CANYON ROAD MALIBU, CA 90265 (310) 317-5250 Funding Agency: Office of Naval Research PR Number: 00PR00237-00 Award Number: N0001499C0144 Current End Date: 08-Apr-2002 Scientific Officer: Deborah Van Vechten Objective: Continue development of Pi Sigma Delta analog to digital converters demonstrated earlier using non ONR funding. This work will demonstrate the most critical component of an ADC, which, once finished, using lower technical risk components, is expected to meet the performance specifications expressed in the AMRFS BAA ONR 98-022 and so enable the concept of reconfigurable, multi-function receive apertures. Approach: Utilize a pi sigma delta analog-to-digital converter architecture consisting of 8 separate delta-sigma-modulator channels employing 4th order modulators clocked at 8GSPS. Different band width modes will utilize different numbers of channels (the narrower the BW, the fewer the channels). The modulator circuit sections will be implemented in 200 GHz fT, fmax low parasitic InP HBT IC technology. The decoder/ digital filter section required for a complete ADC will be implemented in software and the measured data will be processed off-line. A circuit layout database for the pi sigma delta-modulator section will be created and two iterations of this section will be fabricated, packaged in a commercially available high-speed package and tested for functionality in beam steering receivers. Progress: Work on the detailed circuit plans began in late spring 1999. The architecture planned uses a constellation of eight delta-sigma modulator channels clocked at 8 GSPS and combined so that the errors introduced by the modulators must be uncorrelated and cancel. A mathematical model has been developed to allow behavioral simulation of the planned continuous time DS modulators using conventional discrete time simulation tools for the noise transfer function. Title: The Effects of Impurities on Junction Behavior in High-Temperature PI: Michael Flatte UNIVERSITY OF IOWA Physics and Astronomy Address: Iowa City, IO 522421479 (319) 335-0201 Funding Agency: Office of Naval Research PR Number: 00PR00238-00 Award Number: N000149910313 Current End Date: 31-Dec-2001 Scientific Officer: Deborah Van Vechten Objective: Calculate the effect of different classes of impurities in the vicinity of free or interface surfaces on the behavior of superconductors and use the calculational results to explain experimental results of other ONR supported researchers. Approach: Apply the calculational approach for interface electronic structure developed under the previous ONR grant to calculate the supercurrent transport through arbitrary transparency junctions, the effect of strong and potentially time-dependent impurities such as uncompensated spin copper atoms, identify signatures in the IV curves of oxygen vacancies and excess concentration of cobalt atoms. Also include complexity of proper multi-band tight binding models of the band structure into the calculations. Progress: Parametrized versions of multiple electronic bands were included into the calculations of impurity effects on junction behavior. Good correspondence was found with STM measurements by J. C. Davis on impure BSCCO. Work to include the CuO chains also found in YBCO are mostly done and supercomputer time for these more complex calculations has been secured. Title: EXPERIMENTS ON SUPERCONDUCTIVITY AT MICROWAVE AND RADIO FREQUENCIES PI: Nai-Phuan Ong THE TRUSTEES OF PRINCETON UNIVERSITY Physics Dept. Address: FIFTH FLOOR NEW SOUTH BUILDING Princeton, NJ 085440636 (609) 248-4347 Funding Agency: Office of Naval Research PR Number: 00PR00239-00 Award Number: N000149810081 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: To understand the systematics of the truly inherent effects which occur when high temperature superconductors are subjected to simultaneous dc magnetic fields B and rf signals. The plasma resonance(perpendicular to the ab planes) phenomena will be evaluated for use as an absorption based sensor in the 30-300 GHz range. The basic nature of the photon detection process will be clarified by distinguishing thermal conduction by phonons and quasiparticles. An improved scanning microwave absorption probe will allow vortex pinning sites to be unambiguously identified and correlated to the sites of excess energy dissipation in thin film resonators supplied by Lucent Technologies. The work will improve our understanding of the HTS materials and our ability to build low loss, high power transmit, as well as receive, rf filters and more efficient microwave sensors. Approach: The experiments utilizing tilted magnetic fields to demonstrate the existence of plasma resonances will be extended up to 100 GHz and to lower temperatures using cavity techniques and Bi 2212. The determinants of the width and intensity of the resonance will be the chief focus. The same crystals will be used to investigate phonon vs. quasiparticle heat conduction near the phase transition (B field dependent) recently discovered by the PI. A near field scanning microwave absorption sensor will be constructed to operate in the 10-20 GHz range and used to explore the surface of untwinned YBCO crystals and films and submicron spheres of superconductors. This work will be correlated to work of ONR supported theorists. The device will also be used to improve the understanding of losses in YBCO rf filters in the 1-40 GHz band and could help improve tunnel barriers in the ramp edge Josephson junctions used in HTS digital logic. Progress: Detailed field dependence measurements of the thermal conductivity of YBCO have allowed unambiguous separation of the electronic and phononic contributions. The derived quasiparticle (electronic) mean free path increases smoothly from 0.1 micron at 90K to 0.5 micron at 10K. A scanned 25 to 110 GHz microwave spectrometer has been constructed and used to observe for the first time antiferromagnetic (AF) resonance lines in a manganite and cyclotron resonance in a 2D electron gas (GaAs-AlGaAs). Title: Expansion of Josephson Effect & Macroscopic Quantum Interference in Superfluid 3He PI: James Davis THE REGENTS OF THE UNIVERSITY OF CALIFORNIA BERKELEY Department of Physics Address: 366 Le Conte Hall Berkeley, CA 94720 (510) 642-4505 Funding Agency: Office of Naval Research PR Number: 00PR00240-00 Award Number: N000149411008 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: To complete a proof of concept demonstration of a superfluid quantum interference gyroscope having rotational sensitivity approaching 10^-9 of the earth's rotation rate. The goal of the expansion is to improve likelihood of successful completion of N00014-94-1-1008 which is developing a gyroscope predicted to have orders of magnitude with greater sensitivity than any existing unit. Approach: A toroidal shaped container, ultimately measuring a meter in diameter, will be micromachined in Si and interrupted symmetrically by arrays of 0.1 micron pores through a Si3N4 membranes placed across the ring. At each pore the superfluid mass flow equivalent of the Josephson effect in Dayem bridges will be manifested as a phase dependent difference in the flow rates between the arms, induced by the rotation of the torus. By measuring the critical current of 3He flowing in this system of channels, eventually with 1 part in 10^4 accuracy, the rotational phase contribution can be determined. This Sagnac effect should allow the rotational rate of the Earth to be determined. The approach of the expansion is to fund supply of cryogens more adequately so that actual experiments can be conducted for 8 months a year rather than only the 4 month allowed by current funding levels. Progress: The similarities and differences of superfluid 3He and superconducting Josephson junction were investigated: both display Fiske and Shapiro effects and the Current-Phase relation depends on sin (phase difference) near Tc. However, discrepancies appear at low temperatures and the superfluid case displays two intrinsic dissipation processes. Completion of a rotating cryostat and improved acoustic isolation chamber will enhanced the sensitivity of the gryoscope to be demonstrated early in fy00. Title: FUNDAMENTAL PROCESSES IN SUPERCONDUCTING NANOSTRUCTURES PI: Michael Tinkham THE PRESIDENT AND FELLOWS OF HARVARD COLLEGE Department of Physics Address: Pierce Hall Cambridge, MA 02138 (617) 495-3735 Funding Agency: Office of Naval Research PR Number: 00PR00241-00 Award Number: N000149610108 Current End Date: 31-Oct-2001 Scientific Officer: Deborah Van Vechten Objective: To understand the physics that determines the behavior of Single Electron tunneling Transistors (SET) and to work issues such as their connections to the outside world and operating temperatures which will effect their device applicability. These devices have features less than 100 nm in size in 2 if not 3 directions and are dominated by quantum mechanical effects. One dimensional strings of nanoparticles offer the possibility of elevated temperature operation and in any case appropriate size scale leads must be provided. Ultra small grains are revealing for the first time ever the detail of many particle energy states. Andreev reflection is visible and important to the tunneling process in superconducting SET. SET are still in their early stages of development but they are expected to be important in the mid term once commercial drivers push main stream solid state electronics into this size scale. The physics they reveal could halt the historic trend in electronics to smaller and smaller scale devices. Approach: In the smallest grains investigated, both the single particle (electron) energy levels and their perturbations due to the other electrons are directly observable for the first time. Using techniques of self-assembly, it is possible to string together tens of nanoparticles. Doing so allows a single set of electrodes to control a larger signal and thus allows higher temperature operation despite thermal noise. Carbon nanotubes are also being explored as growth templates for direct deposition of wiring in SET circuits and for the physics they exemplify. Superconducting SET continue to be studied in the context of what they reveal about Andreev scattering, a critical effect in the push for new HTS devices. Progress: Extremely small size devices have different electrical performance. Wires 50% smaller in diameter (10 nm) than previously reported displayed a 10^3 wider resistive transition and non-zero residual resistance. This places a lower bound on superconducting wire size. A record charge sensitivity of 10-5 e/Hz has been achieved at 100 kHz in a 1 MHz bandwidth in a cryogenic electrometer. The physics of lightning was used to assemble conducting micron-long chains of ~30 nm diameter particles. Title: SUPERCONDUCTORS IN AN EXTERNAL FIELD PI: Vladmir Kresin U S DEPARTMENT OF ENERGY OAKLAND OPERATIONS OFFICE Department of Energy Address: 1 CYCLOTRON ROAD, MS90-1070 BERKELEY, CA 94720 (510) 486-4126 Funding Agency: Office of Naval Research PR Number: 00PR00242-00 Award Number: N0001498F0052 Current End Date: 30-Oct-2000 Scientific Officer: Deborah Van Vechten Objective: To develop and validate by direct comparison to experimental data a detailed, predictive theory of the high temperature superconductors (HTS). Specifically the role of spin-flip scattering in determining the microwave surface resistance and energy relaxation processes, the mechanism of photoinduced superconductivity, and the importance of 'electronic sound'. The first three topics are directly relevant to improving the performance of these HTS materials in high performance filters, an important Navy application. Approach: Work directly with experimentalists in trying to model the effects observed. The PI has developed a model whereby spin-flipping scattering by magnetic impurities becomes frustrated when the directions of the individual moments becomes correlated. This model will be extended to predict microwave surface resistance and comparison made to data from Wuppertal on the dependence of (and especially reduction in) Rs on applied magnetic field. The role of magnetic scattering on the energy relaxation process which follows high energy absorption events will be investigated jointly with 3 other theorists. The mechanism of long term photoinduced superconductivity will be modeled in conjunction with European researchers. Work will also proceed on the issue of explaining existing heat capacity measurements in terms of the unusual plasmon excitation spectrum caused in part by the anisotropy of the HTS materials. It is anticipated that when NRL experimentalists complete measurements of proximity effect samples of HTS and LTS or semiconducting materials, an active exchange will follow. Progress: Earlier models of the IV of step-edge junctions were successfully generalized to deal with the less damaged interface of bicrystal grain boundary junctions. The effect of an inhomogeneous distribution of critical temperatures on the collective behavior of devices was analyzed and used to explain why overdoped Tl-based cuprates display the magnetic and resistive signatures of superconductivity at different temperatures. The unusual superconducting properties of the borocarbides were understood. Title: A Microscopic Description of the Josephson Junction Interface PI: James Freericks GEORGETOWN UNIVERSITY Physics Department Address: 37th & O Streets Washington, DC 20057 (202) 687-6159 Funding Agency: Office of Naval Research PR Number: 00PR00243-00 Award Number: N000149910328 Current End Date: 30-Dec-2002 Scientific Officer: Deborah Van Vechten Objective: Historically the tunnel barriers of superconducting Josephson junctions have been selected in terms of the fabrication compatibility with the superconductor - no chemical reactivity or interdiffusion, stability at process temperatures, flatness of layers - and simple measures of its electrical properties, especially the resistivity. This approach has not yet worked well for the high transition temperature materials. This award seeks to actually model from first principles electrical transport through a barrier for a variety of materials which are insulating for different physical reasons and to do this for both s and d wave (LTS and HTS) superconductors. Once complete, this work will provide important guidance as to how to select the most appropriate barrier for HTS JJ, important information if the HTS materials are to be applied to Navy relevant high performance signal processing requirements in advanced systems such as AMRFS. Approach: A microscopic lattice model for charge transport which averages over the planes parallel to the interfaces that define the Josephson junction and retains the perpendicular to the interface variation is to be developed. The model will be solved numerically to determine the critical current and the junction resistance. The solution will use either dynamical mean-field theory or more sophisticated methods such as the dynamical cluster approximation depending on the locality of the fluctuations. The model parameters (electron density, electron-electron interaction strength, bandwidth, etc.) and the types of interface (semiconductor, Mott insulator, polaronic insulator, antiferromagnetic insulator, Kondo insulator, etc.) will be varied to determine how to optimize the properties of the Josephson junction for both s and d wave superconductors. Progress: Successfully developed algorithms to predict the temperature dependence of the critical current from the phase difference between the superconductors and the junction resistance. The code (which uses fast continued-fraction representations inmomentum space) is over two orders of magnitude more computationally efficient than conventional Bogliubov-Degennes methods. Testing for doped semiconductor barriers nearly complete; comparison to experiment on InAs devices arranged. Title: Optimization of Jc in BSCCO Tapes PI: Eric Hellstrom THE BOARD OF REGENTS OF THE UNIVERSITY OF WISCONSIN Dept of Materials Sci & Engineering Address: 750 UNIVERSITY AVENUE MADISON, WI 53706 (608) 263-9462 Funding Agency: Office of Naval Research PR Number: 00PR00244-00 Award Number: N000149910323 Current End Date: 30-Jun-2000 Scientific Officer: Deborah Van Vechten Objective: The critical current density of long conductors made of BSCCO 2212 superconductors is much lower than that of short wires. The reason is hypothesized to be the difficulty in achieving interconnected and properly aligned 2212 grains from a melt whose composition is in the single phase regime - the 2212 phase melts incongruently. The goal of this work is to see if starting compositions in the "primary phase" regime (from whose melt 2212 phase crystals form directly) will end up producing well oriented, interconnected assemblies of grains that can support high current density, even though second phase species will necessarily be present. Power applications of HTS materials will be enabled by the work. Approach: Prepare powders with several compositions within the primary phase regime and determine the reaction, liquification and solidification temperatures using thermo-gravimetric analysis. Use quench studies and SEM analysis to monitor the phase evolution and homogeneity of the finished tape. Compare to conventionally processed tapes. Title: A Cryogenic Loop for Cooling Spatially-Separate Electronics Components PI: Reza Shekarriz ADVANCED THERMAL AND ENVIRONMENTAL CONCEPTS INC Address: 11890 Old Baltimore Pike Beltsville, MD 207050000 (301) 931-1449 Funding Agency: Office of Naval Research PR Number: 00PR00245-02 Award Number: N0001499C0145 Current End Date: 15-Jun-2000 Scientific Officer: Deborah Van Vechten Objective: To determine if electro-hydro-dynamical pumping (EHD) can provide the fluid drive required to realize spatially localized cryogenic cooling via substrate channels for both superconducting and optimized semi-conducting chips. Performance goals are 0.1 to 10 W of heat lift at 70-80K and low electromagnetic noise. If successful, the use of high performance cryogenic filters and digital signal processors in spatially constrained settings (such as AMRFS receive arrays) and in close physical proximity to electronics not requiring cooling will be enabled. This will help the Navy derive benefit from the significant advantages these devices offer. Approach: Conduct a feasibility study by constructing a model heat loop in the laboratory which utilizes EHD electrodes in MEMs scale channels as the pump. Test its cooling capacity against an electrical heater as a function of drive voltage in the 0-10V range using nitrogen as a single phase liquid and gas and as a fluid which evaporates at the site to be cooled. Determine the heat lift available and the electromagnetic noise created by the flow. Progress: The prototype pump has been designed and tested at room temperature using a laboratory standard fluid. Plans for testing at GSFC with liquid nitrogen and at low temperatures are well advanced. Title: SPIN INJECTION AT FERROMAGNET - SEMICONDUCTOR AND FERROMAGNET - SUPERCONDUCTOR INTERFACES PI: Mark Johnson NAVAL RESEARCH LABORATORY Materials Science and Technology Division Address: 4555 Overlook Avenue SW Washington, DC 203755320 (202) 404-8485 Funding Agency: Office of Naval Research PR Number: 00PR00246-01 Award Number: N0001400WR20011 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: Work is needed to increase the on-state resistance of an individual mesoscopic magnetoquenched superconducting valve if the read-out of stored value is to be a simple to implement operation. These MMSV may be useful as dense, low power, non-volatile and rad hard memory for superconducting digital circuits if this problem can be solved. Currently the lack of memory with these characteristics forces superconducting logic circuits to utilize semiconducting memory which cannot be located in close proximity to the processors or very small (<4 KB), superconducting memories. Superconducting circuits could thus become much more functional and useful in Naval receivers. Approach: Use N metal overlayer to tune the Tc of the superconducting stripe driven normal by the fringing B field closer to the bias temperature of the memory element. Doing that should increase the volume driven normal in the on state and thereby the resistance in normal state. Progress: Development of the Mesoscopic Magnetoquenched Superconducting Valve (MMSV) device is continuing. Initial Nb samples show a factor of 2 suppression of Ic at 4K which can be made much larger by decreasing the bridge's Tc. Other devices demonstrated switching of the spin polarization by current pulses in write wires and a two magnetic layer variant that has higher potential packing density than the 1 layer projected 1 Mbyte per cm2. Designs are complete for switching speed testing at HYPRES. Title: Doped SrTi03 Films for Josephson PI: John Price THE REGENTS OF THE UNIVERSITY OF COLORADO Department of Physics Address: 206 armory Campus Boulder, CO 803090019 (303) 492-2484 Funding Agency: Office of Naval Research PR Number: 00PR00247-00 Award Number: N000149910360 Current End Date: 31-May-2002 Scientific Officer: Deborah Van Vechten Objective: SrTiO3 (STO) can be shifted from an insulator to a low carrier density (super) conductor by doping with Nb. While pure STO is studied in thin film form due to the utility as its voltage tunable dielectric constant, the doped form is a potential tunnel barrier for YBCO based HTS Josephson junctions. The goal of this award is to test the latter application -an improved junction fabrication process, especially an improved tunnel barrier- which is required if the highly useful digital applications superconductivity enables are to be realized at temperatures much above 10K. Approach: A previous ONR award explored the dopant dependent properties of Nb:STO and learned how to make the films reproducible. This award will develop an SNS HTS junction technology based on YBCO/Nb:STO/YBCO trilayers (which could be etched to define junctions in processes paralleling that of Nb/AlOx/Nb trilayers in LTS) and bilayers (which defines the junction by removing S material). This approach will utilize the low defect density and extreme stability, even to oxygen loss, of Nb:STO and its excellent epitaxial compatibility with both YBCO and substrate materials. Material will be deposited at U Colorado and, in some cases, finished into junctions as part of collaborations with NIST (Benz, Ono) and others who are expert in HTS JJ fabrication and test. Another collaboration with Freericks at Georgetown will help define the physics of tunneling using single devices that can be made to undergo the metal insulator transition and some work will be done to look at FET style devices using bilayer samples. Progress: Nb-doped strontium titanate thin films may enable nm scale bilayer HTS Jospehson junction fabrication. Nb doping the target controllably produces metallic films: carrier concentrations > 1?1019 cm-3 and mobility > 70 cm2/Vs. Ar was added to the deposition system to improve the uniformity of ion bombardment. Hc2T(T) measurements indicate the material is a very low carrier density s wave superconductor, as well as the first example of a thermodynamically stable and field depletable superconductor. Title: RESONANT QUANTUM EXCITATION IN OXIDE SUPERCONDUCTORS PI: T. Venkatesan UNIVERSITY OF MARYLAND AT COLLEGE PARK Department of Physics Address: College Park, MD 20742 (301) 405-7320 Funding Agency: Office of Naval Research PR Number: 00PR00248-00 Award Number: N000149810284 Current End Date: 28-Feb-2000 Scientific Officer: Deborah Van Vechten Objective: To shed experimental light on the relationship between the structure and chemical constituents of the unit cell in real samples (with defects) and the appearance of superconductivity in the high transition temperature materials. The resonant response to optical absorption will be utilized. Approach: To determine whether the recently observed, frequency dependent, enhanced pair-breaking following photon absorption is a true resonant phenomena in YBCO. Then formulate a model of the effect which identifies the causal structural and compositional features and test using other superconductors. Progress: Temperature dependent fine structure in the pair breaking resonance has been detected. The spacing appears to correspond to that expected from antiferromagnetic fluctuations in oxygen depleted regions. The current hypothesis is that the term is from the electronic density phase segregation known as stripes. This hypothesis will be evaluated in the renewal effort. Title: Lumped Josephson Junction Arrays for High Performance Communication, Networking, and Radar PI: Samuel Benz U S DEPARTMENT OF COMMERCE NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY Electromagnetic Technology Division Address: 325 BROADWAY BOULDER, CO 80303 (303) 497-5258 Funding Agency: Office of Naval Research PR Number: 00PR00249-00 Award Number: N0001499F0042 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: Develop the ability to fabricate an electrically "lumped" series array of superconducting Josephson junctions that will enable a super-conducting digital-to-analog converter capable of directly generating arbitrary wave forms with useful voltage amplitudes and phase noise low enough to be useful in Doppler radar. Such units are expected to be able to operate over the range of carrier frequencies and functionalities appropriate to AMRFS. "Distributed" arrays display greater frequency sensitivity and generally poorer performance, especially in regard to the maximum voltage swing. Approach: To act as a lumped element at 20 GHz, the array must occupy less than 2 x 2 microns. Yet to produce by itself a 1 V signal amplitude, that area must contain of the order of 30,000 junctions that work together to produce over 10^14 SFQ pulses per second. Ramp edge HTS junctions are impossibly large. Arrays with a variety of junction spacings will be produced in HTS using both electron and ion beam damage at Cambridge University (separate ONR award). LTS versions using from Nb/PdAu bilayers and e beam written lithography could be made at NIST if essential. Junction uniformity, interactions, and suitability for application to the DAC will be investigated. Progress: A focused ion beam is being used to etch arrays of superconductor-normal metal-superconductor junctions by controllably removing a portions of the top layer of S every 200 nm or less. Small arrays have been fabricated and delivered to NIST using Nb/PdAu bilyers. More complex coupling effects appear for spacings <~150nm. The reproducibly high-quality junctions showed Josephson coupling which scaled qualitatively with barrier properties and temperature as expected. Title: HTS Lumped Josephson Junction Arrays for High Performance Communication, Networking and Radar PI: Mark Blamire UNIVERSITY OF CAMBRIDGE Department of Materials Science and Metallurgy Funding Agency: Office of Naval Research PR Number: 00PR00250-00 Award Number: N000149910146 Current End Date: 30-Nov-2000 Scientific Officer: Deborah Van Vechten Objective: Develop the ability to fabricate an electrically "lumped" series array of superconducting Josephson junctions that will enable a super-conducting digital-to-analog converter capable of directly generating arbitrary wave forms with useful voltage amplitudes and phase noise low enough to be useful in Doppler radar. Such units are expected to be able to operate over the range of carrier frequencies and functionalities appropriate to AMRFS. "Distributed" arrays display greater frequency sensitivity and generally poorer performance, especially in regards to the maximum voltage swing. Approach: To act as a lumped element at 20 GHz, the array must occupy less than 2 x 2 microns. Yet to produce by itself a 1 V signal amplitude, that area must contain of the order of 30,000 junctions that work together to produce over 10^14 SFQ pulses per second. In this work arrays with a variety of the repeat distances between junctions below 100 nm will be produced in HTS using both electron and ion beam damage. Junction uniformity, independence of operations, and suitability for application to the DAC will be investigated. Progress: A focused ion beam is being used to etch arrays of superconductor-normal metal-superconductor junctions by controllably removing a portions of the top layer of S every 200 nm or less. Small arrays have been fabricated and delivered to NIST using Nb/PdAu bilyers. More complex coupling effects appear for spacings <~150nm. The reproducibly high-quality junctions showed Josephson coupling which scaled qualitatively with barrier properties and temperature as expected. Title: HIGH-RESOLUTION ANGLE - AND SPIN-RESOLUTION PHOTOEMISSION STUDIES OF INTERFACE ISSUES OF MAGNETIC AND SUPERCONDUCTING MATERIALS PI: Zhixun Shen THE BOARD OF TRUSTEES OF THE LELAND STANFORD JUNIOR UNIVERSITY Sponsored Projects Address: 125 PANAMA ST JORDAN QUAD BIRCH Stanford, CA 943054055 (415) 723-4659 Funding Agency: Office of Naval Research PR Number: 00PR00251-00 Award Number: N000149810195 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: To improve our understanding of the surface physics of both high temperature superconductors and magnetic materials and the interfaces which form when they are layered on one another. For the magnetic materials, the goal is to determine the angle and spin resolved density of states in the magnetic state and understand how these impact the transport of spin polarized current into overlayers of normal metals. Superconducting materials will then be added to form spin current sensing devices. A second effort will look at the viability of stabilizing the surface states revealed by low temperature cleaving by gaseous passivation. If successful, this could lead to the development of ways of avoiding degraded surface layers in fabricating HTS structures such as the Josephson junctions used in digital electronics. The former effort is part of the DRI on spin-injection devices. Improvements in the quality of circuits delivered to Navy applications requiring high performance electronics such as ship self defense and AMRFS is predicted. Approach: To fabricate extremely high quality samples and measure them extremely accurately. The magnetic/normal metal work will be done by taking high quality single crystals such as Ni and Co, cleaning the surface well, and depositing layers of Cu, Ag, and Au (different spin-orbit scattering) a few atomic layer thick on top. These would then be measured with angle resolved photo-emission (APRES) having 4 meV energy resolution, LEED, and STM in-situ with the deposition at a new facility at the Advanced Light Source. SMOKE will be used to measure the magnetic properties. The surface passivation work has already shown there is a disordering of the well-order bare surface as the temperature is raised. By adding gases to the cleavage chamber and monitoring using ARPES as the temperature is changed, the chemical shifts caused by the adsorbate can be deduced. If any are found that substantially delay the onset of disorder (H is similarly used to passivate dangling bonds in amorphous Si), then industrial contacts will be solicited to intentionally add the reactive species to the deposition environment near the end and after the deposition. Questions to be answered are whether, and how uniformly, the gas is incorporated and with what effect on the electrical properties of subsequently processed devices. The structure of "engineered interfaces" (intentionally oxygen depleted) will also be determined. Progress: The technical problems of introducing ozone into a UHV environment have been solved to the point where degradation of a newly exposed YBCO surface by contaminant water and CO2 is mostly under control. This is a necessary first step toward being able to detect the shifts in surface oxygen states using ARPES and to study potential YBCO passivation structures, the goal of this work. Title: Growth & Microwave Studies of Nonlinear Dielectric Films for Tunable High Temperature Superconductor Microwave Electronics PI: Charles Rogers THE REGENTS OF THE UNIVERSITY OF COLORADO Dept of Physics Address: Boulder, CO 803090019 (303) 492-4476 Funding Agency: Office of Naval Research PR Number: 00PR00252-00 Award Number: N000149710141 Current End Date: 30-Sep-2002 Scientific Officer: Deborah Van Vechten Objective: To enable thin-film capacitors with wide tuning (>30%) and dielectric loss tangents below 2 x 10-4, an order of magnitude better than achieved today. In combination with the small fields required to tune (1 V/mm) STO, these properties will enable wide-band tunable filters and other microwave circuit elements of interest to the Navy in systems such as AMRFS. Approach: The origin of dielectric losses in STO thin films will be understood via a systematic study of film growth conditions, liftoff processes, and their impact on microwave dielectric response. In addition to these processing studies, the dielectric response dependence on temperature, electric field and applied strain will be studied. Progress: Efforts have focused on improving the dielectric properties of STO via optimization of growth conditions and monitoring using in situ optical ellipsometry. The resultant STO films on LAO substrates have the highest dielectric tuning and lowest microwave losses ever reported at microwave frequencies. A method for lifting-off epitaxial films of STO was developed that produced films with twice as large dielectric tuning as the best films on LAO and approaching those observed in bulk STO crystal. The existence of In situ optics allows more rapid reoptimi-zation of growth conditions when chamber instrumentation is altered and essentially needs recalibration. Title: Expansion of "Demonstrations of Ultra-High-Speed and Dense Circuits using Unique Nb IC Fabrication†PI: Theodore Van Duzer THE REGENTS OF THE UNIVERSITY OF CALIFORNIA BERKELEY Regents/Sponsored Projects Address: 336 Sproul Hall Berkeley, CA 94720 ( 51) 064-3306 Funding Agency: Office of Naval Research PR Number: 00PR00308-02 Award Number: N000140010003 Current End Date: 30-Sep-2002 Scientific Officer: Deborah Van Vechten Objective: Will advance state-of-the-art in digital superconducting electronics both in regard to processing speed of minimal sized ADC and ability to realize complex circuits. The clock speed aspect will include fabrication using UCB demonstrated output 10 GHz amplifiers and 10 fold larger Jc devices of circuits designed at Northrop Grumman to provide performance well beyond the Walden curve needed in systems such as AMRFS. The complex circuit will initially be the digital SQUID of SUNY-SB which is expected to strongly enable the application of SQUIDs to medicine, especially heart disease detection, by eliminating the costly (>$1M) need for a magnetically shielded testing environment. Approach: This work will confirm the high device quality possible with an NbN/TaN/NbN layer structure and measure the spread in junction parameters. Since they have much thicker barriers, achieving the <2% parameter spreads needed to yield a functional circuit is expected to be easier than for the currently standard device structure. Title: Noise and Superconducting Devices PI: Clare Yu THE REGENTS OF THE UNIVERSITY OF CALIFORNIA IRVINE Dept. of Physics & Astronomy Address: 115 ADMINISTRATION BUILDING IRVINE, CA 92717 (949) 824-6216 Funding Agency: Office of Naval Research PR Number: 00PR00309-00 Award Number: N000140010005 Current End Date: 30-Oct-2003 Scientific Officer: Deborah Van Vechten Objective: Electrical noise in the circuit is the factor which limits the detection range and sensitivity of SQUID sensor based systems such as the unexploded ordnance finding system of NCSC-Panama City. At the other extreme of frequency, phase noise may limit the functionality of high speed digital systems. This award will devise ways to remove the current error of factors of 10 or more from predictions of noise performance based on fundamental theory and provide guidance to improving performance. Approach: This small scale effort will start by reviewing the literature on noise in SQUIDs and simulations of bit error rates and other manifestations of digital phase noise. Then the theoretical literature will be surveyed to find the most relevant fundamental research. Finally these existing theories will be combined to produce a predictive model and the result compared to existing noise data. Title: Microwave Losses in Tunable Device PI: S. Sridhar NORTHEASTERN UNIVERSITY Distinguished Professor of Physics Address: Physics Dept Boston,, MA 02115 (617) 373-2930 Funding Agency: Office of Naval Research PR Number: 00PR00310-00 Award Number: N000140010002 Current End Date: 30-Sep-2002 Scientific Officer: Deborah Van Vechten Objective: To increase the performance advantage of superconducting rf filters by testing a magnetic loss hypothesis and, if proven, frustrating the loss mechanism. The resultant materials improvement will make such HTS filters the obvious candidates for use in Navy multifunction rf systems such as AMRFS. Approach: The possible relationship between microwave loss and non-linear behavior and the motion of fluctuating localized regions of antifer-romagnetic order within globally superconducting samples will be explored. If a causal relationship is proven to exists, methods of reducing the undesirable behavior will be devised. Title: Process Development for High Speed Superconductor Logic PI: James Lukens THE RESEARCH FOUNDATION OF THE STATE UNIVERSITY OF NEW YORK AT STONY BROOK Department of Physics Address: W-5510 MELVILLE LIBRARY STONY BROOK, NY 117943300 (516) 632-8081 Funding Agency: Office of Naval Research PR Number: 00PR00319-00 Award Number: N000149910374 Current End Date: 28-Feb-2002 Scientific Officer: Deborah Van Vechten Objective: To dramatically increase the clock speed at which moderately complex Nb Josephson junction circuits have been demonstrated to operate. The world's record circuit speed of 770 GHz, ~10X the fastest demonstrated semiconductor circuit, was done for a quite simple divide-by-2 circuit. Success in this effort will allow technology transfer to industry and an increase in clock speeds from about 15 GHz today for useful circuits such as ADC to about 100 GHz. Once there, they will be of great utility to systems such as AMRFS that want to process wide ranges of the electromagnetic spectrum at one time and without any frequency down-conversion. Approach: To improve the process spreads and design rules as the linewidth is shrunk first to 1.5 microns and then 0.8 microns, and finally to 0.5 or less. At each stage work to increase the complexity of the circuit demonstrated without deteriorating the yield. Progress: The initial goal of the ADC critical components demonstration has been defined to use junctions 1 micron on a side. The resultant devices will have junction areas nearly an order of magnitude smaller that those made with present HYPRES technology. Initial discussions of design rules were conducted and an initial fabrication run this summer at Stony Brook based on HYPRES circuit layouts planned. Title: Ka-band HBT Phased Array Technology PI: Marko Afendykiw NAVAL AIR WARFARE CENTER WEAPONS DIVISION RF Guidance & Analysis Branch Address: Code 087 China Lake, CA 935556001 (619) 939-2845 Funding Agency: Office of Naval Research PR Number: 00PR00371-00 Award Number: N0001400WR20050 Current End Date: 30-Sep-2000 Scientific Officer: John Zolper Objective: This work seeks means of providing high performance amplifiers at 40 GHz and below with acceptable 1/f noise figures to be used in missile tracking and intercept E/M systems. Specific objectives include an output power of 1.5 watts at 30% duty cycle, 200 nanosecond pulse width, and 24 db gain with 30% power added efficiency. The effort is divided between industry and in-house. Approach: GaAlAs:GaAs heterojunction bipolar transistors will be designed and tested. Performance will be optimized by achieving higher gain via a better tradeoff between collector transit time and breakdown voltage and by reducing parasitic capacitance between collector and base regions. Further improvement will be achieved by better thermal design. Contract effort is focused on device topological configuration improvements to reduce parasitics and the use of InP/InGaAs to achieve power and low noise in a single material and device type. In-house the approach has been to develop extensive testing and evaluation of the HBT technology that is being developed. Test capabilities include linear and non-linear network analysis, on-wafer characterization and passive load-pull system. Progress: During this period collector under cut AlGaAs/GaAs HBTs were modelled and tested. Modelling shows the expected improvement in the maximum frequency of oscillation, however; this was not seen experimentally in the large signal power or gain. The speculation was that the lack of experimental improvement was due to reduced thermal properties of the under cut HBT. Work was also initiated on an InGaP collector HBT that should offer superior performance over the AlGaAs/GaAs device due to better breakdown and surface properties. Title: Frequency Converters PI: Dean Nathans SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO NCCOSC RDTE DIV Address: Naval Command, Control & Ocean Surveillance Center San Diego, ca 921525001 (619) 553-1283 Funding Agency: Office of Naval Research PR Number: 00PR00372-01 Award Number: N0001400WX20045 Current End Date: 30-Sep-2000 Scientific Officer: John Zolper Objective: To develop integrated circuits implementing L-band and higher microwave band functions for high rate communications, sensor and information systems. A reduced size(MMIC) synthesizer with low phase noise is desired for use in UAVs. The synthesizer should provide for the possibility of incorporation of frequency hopping capability. Also desired is a miniaturized RF translater that through monolithic integration(bandpass filters, RF preamp, mixer, l.O., IF filter/amp) would produce a common module that could be used in multiple receiver spread spectrum TDMA systems such as JTIDS and MIDS. Approach: The frequency synthesizer exploits GaAs X-band HBT MMIC technology together with a commercially available phase detector IC. The RF translater is also expected to exploit MMIC technology. Progress: The contract to Hittite is continuing with a modified design to reduce the fabrication cost of the monolithic RF translator. Cost sharing from the MIDS program office was negotiated and the funding level from ONR was adjusted to move the program forward. Title: MICROWAVE TUNABLE ACTIVE FILTERS PI: Christen RAUSCHER NAVAL RESEARCH LABORATORY CODE 6851 Address: NAVAL RESEARCH LABORATORY WASHINGTON, dc 203755347 (202) 767-3526 Funding Agency: Office of Naval Research PR Number: 00PR00373-00 Award Number: N0001400WR20016 Current End Date: 30-Sep-2000 Scientific Officer: John Zolper Objective: Develop techniques to realize compact, highly-selective tunable microwave filters for use in high-dynamic-range, multifunction transmit-receive and receive-only modules. Approach: Will focus on two main tasks: 1) the derivation and experimental demonstration of improved circuit architectures and 2) the development and demonstration of an improved semiconductor varactor technology. Progress: Work has concentrated on demonstrating a new low-loss heterostructure varactor for use in a tunable notch filter, and on developing a suitable test bed for verifying device performance. After extensive computer simulations, heterostructure material was grown to specification by MBE, comprising 15 layers of 50 Angstrom thick Si-doped GaAs interleaved with 1000 Angstom thick layers of undoped AlGaAs. The test-bed circuit encompasses two frequency-tunable bandpass filters separated by an MMIC amplifier, and is designed to maintain constant instantaneous bandwidth across the tuning range. Varactors and test filter are in the final stages of fabrication and assembly, respectively. Work has focused on the realization of heterostructure varactor diodes for use in a tunable notch filter, and on the development of a suitable test-bed circuit for verifying device performance. Two diode fabrication runs were completed, employing layered GaAs-AlGaAs material grown previously by MBE. A tunable active bandpass filter, to serve as test bed, was successfully implemented in hybrid-integrated-circuit form. The circuit was tested, using conventional GaAs varactor diodes. As predicted, the response maintained a constant absolute passband width across the specified 6-7 GHz tuning range. Title: ULTRA HIGH SPEED InP BASED E/D HEMT ANALOG TO DIGITAL CONVERTERS PI: Ilesanmi Adesida THE BOARD OF TRUSTEES OF THE UNIVERSITY OF ILLINOIS AT URBANA CHAMPAIGN DEPARTMENT OF ELECTRICAL & COMPUTER ENGR. Address: 208 N. WRIGHT STREET URBANA, il 61801 (217) 244-6379 Funding Agency: Office of Naval Research PR Number: 00PR00374-00 Award Number: N000149810376 Current End Date: 28-Feb-2001 Scientific Officer: John Zolper Objective: To demonstrate A/D converters with state-of-the-art InP based high electron mobility transistors. Approach: InP based enhancement and depletion mode HEMTs will be fabricated using selective recess etching to achieve high performance and high yield A/D circuits. Progress: Work has focused on improving the performance of enhancement-mode InAlAs/InGaAs/InP HEMTs. Whereas previous work on HEMTs utilized heterostructures with electron sheet density of 0.7E+12 cm-3, new layers have a sheet density of 1.0E+12 cm-3. The aim is to enhance the unity current-gain cut-off frequency to well over 100 GHz. A novel Pt/Mo gate metallization is being developed for the E-mode HEMTs in order to ensure a reliable self-limiting Pt reaction with InAlAs for a more uniform threshold voltage. This will also allow a single-step annealing process for the gate and ohmic metallizations. Work has commenced on developing realistic circuit models for HEMTs. Simple circuits have been designed and laid out consisting of differential pairs of E/D HEMTs in order to determine device matching characteristics. Title: Wide Bandgap Broad Bandwidth HBT Amplifiers PI: William Schaff CORNELL UNIVERSITY Department of Electrical Engineering Address: 415 Phillips Hall Ithaca, NY 14853 (607) 255-3974 Funding Agency: Office of Naval Research PR Number: 00PR00375-00 Award Number: N000149810015 Current End Date: 14-Oct-2000 Scientific Officer: John Zolper Objective: To develop and demonstrate heterostructure bipolar transistor (HBT) amplifiers with required bandwidth, linearity, and efficiency. The dominant element in development of these amplifiers will be the capabilities of the HBT. This program will develop a GaN-emitter SiC-base-collector HBT suitable for meeting high performance amplifier requirements. While the high temperature capability of wide bandgap transistors required for high power operation is known, HBT device parasitics need to be minimized for amplifier applications. Approach: Both materials growth and device process developments will be undertaken to develop a high performance GaN/SiC HBT. Starting with commercially available SiC epitaxial layers of the the collector and subcollector, additional SiC and/or GaN layers will be grown by either chemical vapor deposition or molecular beam epitaxy. High level p-type doping of SiC, as required for the HBT base, will be developed via either epitaxial growth or ion implantation. Flip chip bonding will be applied to the HBT to optimize heat removal from devices during high power operation to enhance circuit efficiencies. Class B power amplifier will be developed based on the proposed HBT. The amplifiers will be designed to minimize backward wave propogation on the trans-mission line. This will involve new circuit design approaches. Progress: Modelling was performed of WBG HBT DC characteristics. Developed alternative HBT designs to include piezoelectric effects. Developed single step techniques for epitaxial growth of GaN on SiC for formation of GaN emitters on a SiC base and collector. Began fabrication of Base-Collector diodes to characterize deep levels in p-SiC which might limit electron lifetimes and HBT gain. Began design of HBT process including: layout of e-beam lithography masking for cascade probe RF HBT transistors and characterization of dry etching. The project remains on schedule. Established spontaneous and piezoelectric effects in AlGaN/SiC base-emitter junction designs. Began process development to address the polarization effects -patterned base mesas to extend nitride critical thickness AlGaN emitters to raise valence band offset for 4H SiC heterostructures. Began evaluation of nitride/carbide inter-face intermixing. Conceived a wafer bonding process to mate N-face GaN with Si-face SiC. -------------------------- More ----->
[Edited 1 times, lastly by Alpha-Theta on 07-25-2002]

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Alpha-Theta
Superior

ª×µ»ƒ³²² 694 posts, May 2002
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posted 06-07-2002 02:21 PM
Title: High Resolution Transferred-Substrate HBT Microwave / RF ADCs PI: Mark Rodwell THE REGENTS OF THE UNIVERSITY OF CALIFORNIA SANTA BARBARA Department of Electrical and Computer Engineering Address: CHEADLE HALL ROOM 3227 Santa Barbara, CA 93106 (805) 893-3244 Funding Agency: Office of Naval Research PR Number: 00PR00441-00 Award Number: N000149810830 Current End Date: 31-Aug-2001 Scientific Officer: Deborah Van Vechten Objective: Seeks new approaches to versatile analog to digital converters wherein the resolution-bandwidth relationship can be dynamically reprogrammed and wherein new low parasitic heterojunction bipolar transistors are employed to increase performance. Approach: Low parasitic, transferred substrate heterojunction bipolar transistors will be used with deep submicron lithographic resolution and connected in a delta-sigma configuration. Progress: UCSB has completed definition of the operating parameters and detailed design of the individual subcircuits of a >20 GHz clock, single-bit quantizer based, delta- sigma design. Masks layout (4 ADC design variants) used up to 350 HBTs. Distortion cancellation techniques were invoked to insure the needed SFDR and the electroplated copper substrate perfected to dissipate sufficient heat. Fabrication and testing has begun. UCSD has begun work on mismatch-shaping DACs with reduced gate count. Title: Multifunction Wideband, High Resolution, 1 GHz Analog-Digital Converter (ADC) PI: William Skones TRW INCORPORATED SPACE AND TECHNOLOGY DIVISION Electronic Systems Group; M/S M5/1454 Address: One Space Park Redondo Beach, CA 90278 (310) 813-2420 Funding Agency: Office of Naval Research PR Number: 00PR00442-02 Award Number: N000149920004 Current End Date: 30-Mar-2002 Scientific Officer: Deborah Van Vechten Objective: Develop a hybrid ADC consisting of a new 3 bit sigma delta ADC composed of high fT InP HBTs with the loop residual sampled by a 9 GaAs Nyquist Subranging ADC developed under other government contracts. This ADC is expected to meet the performance specifications expressed in the AMRFS BAA ONR 98-022 and so enable the concept of reconfigurable, multi-function receive apertures. Approach: Use a hybrid architecture to achieve the high SINAD of sigma delta ADCs and the high SFDR of a Nyquist ADC without going to the very high sample rate required in a pure sigma delta design. Utilize both the current state of the art Ft>100 GHz InGaAs/InAlAs/InP IC technology and the >200 GHz improvement currently under ONR funded development. Correct the DAC errors outside the loop and work hard to improve the loop filter performance. FPGA will be used in the back end combining logic to prove the design before custom ASIC production. Progress: The initial iteration of design work has nearly completed the detailed circuit designs. HBT device improvement continues with toggle flip flops executing at above 65 GHz. Title: A Study of the Switching Speed of Magnetoquenched Superconductive Devices & their Applicability to Practical Superconductive Electronics PI: Steven Kaplan HYPRES INC Address: 175 Clearbrook Rd Elmsford, NY 10523 (914) 592-1190 Funding Agency: Office of Naval Research PR Number: 00PR00444-00 Award Number: N0001499C0128 Current End Date: 31-Dec-2001 Scientific Officer: Deborah Van Vechten Objective: Mesoscopic Magnetoquenched Superconducting Valves (MMSV) were demonstrated using lead for the superconductor in fy98 at NRL under ONR support. These devices are a leading possibility for on-chip memories for use with niobium (Nb) based digital circuits operating in 100 GHz SFQ logic systems at 4 K. The objective of this effort is define more clearly the set of requirements for such memory and help evaluate the MMSV and other magnetic concepts. The devices are needed for the proposed petaflop computer to provide low power, fast cache memory close to the central processors, a function currently without good candidate devices. They also could be used in high fidelity DRFM applications and in the beam/function control portions of the AMRFS system. Approach: The approach is to work with Dr. Johnson of NRL and Prof. Beasley at Stanford to jointly test the viability of alternative magnetic memory devices for 4K digital systems. HYPRES will facilitate fabrication of niobium MMSV devices by providing wafers with Nb films on ground planes to NRL as needed and collaboratively design masks for high speed tests of the basic devices, to be done at HYPRES. Dr Kaplan will help Dr Beasley define the requirements of a memory device used by and near a high speed (100 GHz) SFQ superconducting circuit. Suitable probes will also be designed (8 high speed and multiple low speed lines) and purchased for use in testing at both NRL and HYPRES. Progress: Designs have been iterated and are ready for fabrication. New probe is on order. Title: Low-Loss High Speed Tunable Filters PI: Salvador Talisa NORTHROP GRUMMAN CORPORATION Address: PO Box 746 MS 1110 Baltimore, MD 21203 (410) 993-2910 Funding Agency: Office of Naval Research PR Number: 00PR00445-00 Award Number: N0001499C0157 Current End Date: 30-May-2001 Scientific Officer: Deborah Van Vechten Objective: To demonstrate room temperature pass band filters that can be switched as to center frequency by a set of MEMS actuated capacitors in combination with printed inductors. Units with 16 center frequencies in the 1-5 GHz band will be demonstrated, but preliminary designs for the 4-20 band will also be produced. Critical parameters include insertion loss <0.5 dB so that they can be used before the LNA in receivers, TOI >60 dB because there will be multiple signals received by every element, and switching times less than 1 microsecond. Low cost and MMIC compatibility are also requirements. These filters are needed to achieve adequate isolation in the AMRFS multiple simultaneous function context. Approach: The MEMS switches and filter designs have already demonstrated sufficient Q, TOI, power handling, and low insertion loss and LTCC is an appropriate packaging material. Similar switches have shown no failure after the equivalent of 10 yrs of switching every 200 microsec. What is most required is to decrease the MEMS switching time from a few microsec to less than 1 by modifying the geometrical design of the fixed electrode and its interaction with the moving electrode and shaping the control pulse. Measurements will be made of the noise added by these passive devices, but is expected to be low. Progress: This effort will combine MEMS, fixed lumped-element filters and low-temperature cofired ceramic (LTCC) packaging. The initial work will demonstrate switchable tuning of high Q filters using MEMS and proprietary miniature (lumped) inductors. Title: DENSELY PACKED ARRAYS FOR ANTI-JAM GPS PI: Donald Bowling NAVAL AIR WARFARE CENTER WEAPONS DIVISION Weapons Division Address: China Lake, CA 935556001 (760) 939-3089 Funding Agency: Office of Naval Research PR Number: 00PR00446-01 Award Number: N0001400WX20392 Current End Date: 30-Sep-2000 Scientific Officer: Deborah Van Vechten Objective: GPS receivers are one of the important applications where typical units lack sufficient size to deploy conventional halfwave length antennas due to the relatively large wavelength of the frequency used. This effort seeks to develop densely packed arrays of electrically small elements capable of active null steering to provide maximal protection against jamming. Approach: The effort will focus on alternative designs for densely packed arrays of electrically small elements that would fit within the 4 inch footprint of already deployed F-18 units. A capability to switch from omni-directional sensitivity to a mode where pattern nulls are dynamically pointed at jammers will be designed in. Selected designs will be simulated using IE3D and Aerospace Corp. adaptive beam steering capabilities program. The best design will then be fabricated in both normal metal and high temperature superconductors. Testing in TEM cell will determine both whether the design functions as expected and how much of a performance advantage the HTS version offers. A digitally beam-formed densely packed array will be demonstrated, with integrated cryocooler if HTS, by the end of the program. Progress: Sequential scanning of linear arrays is the basic element in the production of virtual doppler effects. Issues of mutual coupling of elements and the effect of various smoothing functions on the power spectral density were studied. Hardware construction is complete and tests begun to confirm the simulations using a 12 element array. Title: 100 nm Fabrication Science and TFSOS/SOI Device R&D PI: Isaac Lagnado SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO Center RDT&E Division (NRaD) Address: SAN DIEGO, CA 921525000 (619) 553-2682 Funding Agency: Office of Naval Research PR Number: 00PR00447-00 Award Number: N0001400WX20105 Current End Date: 30-Sep-2000 Scientific Officer: Ingham Mack Objective: Develop an advanced high speed, low power, and high density integrated circuit technology with feature sizes that are readily down-scalable to the 0.18-0.10 micron regime based on the use of ultra-thin, fully depleted silicon films on sapphire. This inherently radiation tolerant technology will be used to enhance reliability, cost effectiveness, and performance of current and future Navy systems. Approach: Techniques to realize CMOS devices with channel lengths <0.25um will be developed using fully depleted thin-film silicon-on-sapphire (TFSOS) technology. Use of Si/Ge and operation at cryoelectronic temperatures (77K) will be investigated to enhance device performance. TFSOS technology will be the basis for implementing A/D converters, artificial neural networks, and UHF/L band transceivers for communications applications. Title: High Power Electronics Building Block (PEBB) - Programmable High Density PEBB Power Supply PI: Isaac Lagnado SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO Center RDT&E Division (NRaD) Address: SAN DIEGO, CA 921525000 (619) 553-2682 Funding Agency: Office of Naval Research PR Number: 00PR00448-00 Award Number: N0001400WR20049 Current End Date: 30-Sep-2000 Scientific Officer: Ingham Mack Objective: Develop technology for providing the manufacturing and commercialization base for a power supply technology for the Power Electronic Building Block (PEBB) with high power density (>150-200 watts per cubic inch), low profile (<0.2 in) and programmable multiple low voltage outputs that are immune to the harsh EMI environment expected from the PEBB. Approach: Techniques to realize high efficiency, high power density, low output power will be developed by use of a soft switched power converter topology. Techniques for the power supply to operate in a high EMI environment will be developed by use of electrostatic shielded matrix magnetics. A low volume, low profile supply will be developed through use of a high operating frequency (>2 MHz) for passive component size reduction and chip-on-board packaging. This program will be partially funded by the Electronics Program and partly by the PEBB Program. Title: Workshop on Doping, Dopants and Low Field Carrier Dynamics in Wide Gap Semiconductors PI: Alexander Scott TMS Structural Materials Division Address: 420 Commonwealth Drive Warrendale, PA 150867514 (724) 776-9000 Funding Agency: Office of Naval Research PR Number: 00PR00449-00 Award Number: N000149910766 Current End Date: 30-Jun-2000 Scientific Officer: Colin Wood Objective: To address transport problems in wide gap semiconductors. Approach: By assembling experts in the field it is expected that possible solutions will be rapidly identified. Title: Electron Emission from cBN & Related Wide Bandgap Systems PI: Roy Clarke THE REGENTS OF THE UNIVERSITY OF MICHIGAN Applied Physics Program Address: H. M. Randall Laboratory of Physics Ann Arbor, MI 481091120 (734) 764-4466 Funding Agency: Office of Naval Research PR Number: 00PR00450-01 Award Number: N000149910337 Current End Date: 31-Dec-2002 Scientific Officer: Colin Wood Objective: Seeks to better understand the crystalline defects in cubic boron nitride so as to better exploit this new material system for enhanced electromagnetic system applications. Approach: Cubic boron nitride films will be synthesized on lithographically defined field tip arrays on single crystalline silicon at the University of Michigan. These films will then be analyzed by x-ray scattering, cathodoluminescnce, RHEED and related tools to determine the nature of defects in the material. Progress: The first task of the project, testing of the UHV cold-cathode emission station, has been accomplished according to the proposal timetable. The second task, to characterize emission from silicon field emitter arrays in collaboration with Pang's group, is also successfully accomplished within the proposal timeline. The third task, to coat these arrays with cubic boron nitride for improved emission characteristics, is underway. Being explored is self-assembled nano-tip arrays as a cheaper and more convenient alternative to conventional lithography. We have formed a collaboration with Dr. Kevin Jensen (NRL) and Jim Severns (Praxis) to transfer some of the UM's coated nano-tip technology to their field emitter array program for space applications. One student supported by the grant has graduated with a Ph.D. during this reporting period and has taken a position as Staff Scientist with Seagate Technology. Title: A STUDY OF GROWTH MORPHOLOGY AND DEFECT GENERATION IN ALUMINUM NITRIDE CRYSTALS GROWN BY SUBLIMATION PI: James Edgar KANSAS STATE UNIVERSITY Department of Chemical Engineering Address: Durland Hall Manhattan, KS 665065102 (785) 532-5584 Funding Agency: Office of Naval Research PR Number: 00PR00452-00 Award Number: N000149910104 Current End Date: 30-Nov-2001 Scientific Officer: Colin Wood Objective: To investigate unique and efficacious means of preparing semiconductor grade aluminum nitride single crystals. Approach: Crystals to be grown by sublimation under reduced nitrogen atmospheric pressure at temperatures in excess of 2250C. Progress: Thick films of AlN have been grown as a first step to bulk crystal growth. Future research is aimed at improving lifetime of equipment against degradation by aluminum at high temperatures. Once this is solved there are no forseen obstacles to growth of commercial scale AlN semiconductor substrates. Title: Novel Deposition and Characterization of Cubic Boron Nitride Films by MOCVD Method PI: Gary Harris HOWARD UNIVERSITY Office of Research Administration Address: 2400 Sixth St., NW Washington, DC 20059 (202) 806-6595 Funding Agency: Office of Naval Research PR Number: 00PR00454-01 Award Number: N000149710935 Current End Date: 31-Jul-2000 Scientific Officer: Colin Wood Objective: To prepare single crystal semiconducting (cubic lattice) boron nitride (BN) for use in ultra-violet countermeasures. Approach: Metal organic vapor phase depostion (MOCVD) will be used to epitaxially grow epitaxial films on thin buffer layers with close lattice match, such as AlN, or AlP. Progress: The epitaxial growth of boron nitride and aluminum boron nitrides have been carried out employing low-pressure chemical vapor deposition methods. Both (0001)sapphire and (100) silicon have been used as substrates. Atomic force microscopy, Auger electron spectroscopy, Hall mobility measurement and X-ray diffraction studies have been performed to characterize the layers. AES data confirm the deposition of both AlN and BN layers on Si with roughness less than 10 nm. The layers are currently polycrystalline. Currently growth conditions are being optimized to improve the crystalline quality desirably to cubic structure. Title: DEVICE PROPERTIES OF SiGeC ALLOYS AND HETEROJUNCTIONS PI: James Kolodzey UNIVERSITY OF DELAWARE Department of Electrical Engineering Address: 77-79 East Delaware Avenue Newark, DE 19716 (302) 831-1154 Funding Agency: Office of Naval Research PR Number: 00PR00456-00 Award Number: N000149310393 Current End Date: 28-Feb-2000 Scientific Officer: Colin Wood Objective: To experimentally determine the physical and electronic properties of Si(1-x-y)Ge(x)C(y) and how they vary with compositional parameters; understand the results in terms of conventional semiconductor energy band theory; and assess the suitability of the material for electronic and optoelectronic device appplications. Approach: Layers of Si(1-x-y)Ge(x)C(y) will be grown using PECVD and MBE. Their properties will be characterized using physical, electrical, and optical measurements. Heterojunctions and heterojunction device structures will be fabricated and characterized. Progress: It was found that the optimum substrate temperature for good surface morphology was 600 C for SiGeC alloys, and 450 C for GeC alloys. The optical absorption coefficients of SiGeC and SiGeCSn alloys were determined using FTIR. It was found that the absorption edge near the bandgap energy varied with composition, but not linearly. It appears that the addition of C increases the bandgap energy for Ge-rich alloys - but this finding is controversial because other groups (Princeton, ASU) claim C decreases the bandgap, therefore; this result is being checked. The discrepancy may be that samples used in the present work are thick and relatively strain-free whereas groups claiming C decreases bandgap reported on thin strained layers. A SiGeC/Si p-n heterojunction diode was fabricated with nearly ideal current-voltage characteristics, and significant photoresponse. The hole mobility in SiGeC and GeC was found to be higher than in pure Si by a factor of three. Title: INVESTIGATION ON NITRIDE SEMICONDUCTORS ON ZnO SUBSTRATES AND ZnO HETEROSTRUCTURES PI: Hadis Morkoc VIRGINIA COMMONWEALTH UNIVERSITY Dept. of Electrical Engineering & Physics Address: 601 West Main Street Richmond, VA 23284 (217) 333-0722 Funding Agency: Office of Naval Research PR Number: 00PR00457-00 Award Number: N000149810139 Current End Date: 30-Nov-2000 Scientific Officer: Colin Wood Objective: To improve epitaxial nitride semiconductor films to be suitable for exploitation as high power microwave devices for military systems. Approach: Zinc oxide substrates will be used instead of the less well lattice matched sapphire or SiC. Progress: Inversion domain free GaN may be grown on ZnO which decomposes at high temperatures and under ammonia, necessitating a low temperature GaN buffer layer grown with RF activated N source. A new MBE system has been installed; characterized GaN films on inexpensive Si substrates are studied; installed an EPI RF source; obtained ZnO substrates from Cermet, albeit a-plane, and are acquiring c-plane substrates from Air Force Research Laboratories. Soon, we will be well positioned to begin growing GaN films on ZnO substrates. Title: ADVANCED MATERIAL INTEGRATION FOR Sb-BASED BIPOLAR TRANSISTORS PI: Karl Hobart NAVAL RESEARCH LABORATORY ES&T Division Address: ES&T Division Washington, DC 203755347 (202) 404-8542 Funding Agency: Office of Naval Research PR Number: 00PR00458-00 Award Number: N0001400WR20048 Current End Date: 30-Sep-2000 Scientific Officer: Colin Wood Objective: Endeaver to wafer bond antimonide semiconductor films and ICs to SiC polycrystaline silicon carbide substrates.This will allow low parasitic, high thermally stable electronics for true time delay microwave radar systems. Approach: Will use Vander Waals forces between extremely flat and polished surfaces at moderate temperature. Under vacuum conditions, and with correct chemical surface treatment most materials will bond very strongly to each other. Using undercutting of base films it is expected that semiconductor structures for ultra fast devices and circuits will develop in this program. Progress: A new source of high resistivity (>10^5 ohm-cm)100mm diameter poly-crystalline SiC has been determined and substrates have been procured; these poly-SiC substrates have been successfully polished to <0.2 nm rms roughness for bonding; the Smart-Cut process for GaSb has been optimized for cleaving temperature and damage reduction; GaSb substrates coated with APCVD SiO2 are presently being polished by CMP to prepare for bonding. Title: Direct Digital SynthesizerULTRA HIGH SPEED DDS FOR ELECTRONIC BEAM STEERING PI: Augusto Gutierrez TRW INCORPORATED SPACE AND TECHNOLOGY DIVISION Electronic Systems & Technology Funding Agency: Office of Naval Research PR Number: 00PR00471-01 Award Number: N0001498C0111 Current End Date: 08-Jul-2001 Scientific Officer: Max Yoder Objective: This work seeks the direct digital synthesis and modulation of RF signals to 18GHz. Approach: Low parasitic heterojunction bipolar transistors will be exploited to develop logic capable of operating from a 100 GHz low phase noise clock. Progress: Excellent progress has been made in InP DHBT technology during this year. A viable production solid source phosphorus technology was developed as it was necessary to achieve maximum analog performance with ultra high frequency. Excellent InP DHBT devices with > 800v Early voltage were developed as necessary for precision DAC current sources. The contractor also developed an initial undercut collector etching capability using the anisotropic etching characteristics of InP which will allow them to achieve minimum collector-base capacitance while simultaneously providing low base resistance. This approach will provide the device performance for a producible high analog LSI yield THz HBT for the 100 GHz DDS. Progress has been made on undercut InP DHBT technology. The recent lots have demonstrated greater current handling and high ft, and fmax > 190 GHz. The undercut devices have yielded the world's fastest digital circuit, a static frequency divide by 2 prescaler operating to > 63 GHz. This was achieved while dissipating only 63 mW of power in the core divider circuit. Although this was the first design with preliminary models, the divider design simulation matched the measured circuit performance to within 10%. Based on these results DDS architecture design has begun and the continuation of improvement on MBE profile and process to improve ft, and fmax. Title: Analog to Digital Conversion PI: Isaac Lagnado SPACE AND NAVAL WARFARE SYSTEMS CENTER SAN DIEGO Center RDT&E Division (NRaD) Address: SAN DIEGO, CA 921525000 (619) 553-2682 Funding Agency: Office of Naval Research PR Number: 00PR00477-01 Award Number: N0001400WX20104 Current End Date: 30-Sep-2000 Scientific Officer: Ingham Mack Objective: Develop technology for providing high performance, low power, radiation tolerant analog-to-digital converters that can be used in Navy surveillance, EW, and communications systems applications. Approach: Analog-to-digital converters using CMOS fully depleted thin-film silicon-on-sapphire technology with feature sizes <0.25um will be utilized to implement A/Ds with sigma-delta as well as flash architectures. Current emphasis is on the development of a 16 bit, 125 MSPS ADC using the sigma-delta approach for applications to ASW. A 4-bit, 20 GSPS ADC using T-gate and SiGe devices will serve as the quantizer for a 10-bit, two-step flash, 2.5 GSPS ADC for surveillance and EW applications. Development of an 18 bit, 100 KSPS, 1 mW ADC will be pursued to meet the demands of on-site signal processing in unattended, remotely controlled systems. Title: Resonant Quantum Excitation in HTS: A Probe of the Striped Phase and Its Influence on Microwave Properties PI: T. Venkatesan UNIVERSITY OF MARYLAND AT COLLEGE PARK Department of Physics Address: College Park, MD 20742 (301) 405-7320 Funding Agency: Office of Naval Research PR Number: 00PR00478-00 Award Number: N000140010028 Current End Date: 31-Dec-2002 Scientific Officer: Deborah Van Vechten Objective: To determine if phase segregation of electrons in high temperature superconductors into dynamically fluctuating antiferromagnetic and superconducting regions is the source of the observed resonant pair breaking effect and of the nonlinearities which result in inter-modulation distortion in HTS filters. If so, the optical measurements can be used to create overwhelmingly superior materials (IP3>100 dB) for use in Navy multifunction rf systems such as AMRFS. Approach: Fabricate thin film samples of materials expected to have wide range of behavior of stripes (parent antiferromagnets, plane vs chain doped YBCO, 214 LSCO with stripes stabilized by Nb doping and under varied stress due to substrates). Measure optical response and correlate to microwave loss measurements of Sridhar, IP3 measurements at NIST, and previous studies of psuedogap. Use silver doped YBCO to test Mannhart's assertion that antiferromagnetic regions exist in grain boundaries by reducing the number of grain boundaries. The PI will produce the samples needed for his own and collaborators efforts. Title: Theory of Transport Processes in Nitride Structures PI: Brian Ridley UNIVERSITY OF ESSEX Department of Physics Address: Wivenhoe Park Colchester, VA 222175660 (607) 256-4369 Funding Agency: Office of Naval Research PR Number: 00PR00479-00 Award Number: N000149910014 Current End Date: 30-Sep-2000 Scientific Officer: Colin Wood Objective: PI will calculate and model electrical carrier transport at low and high electric fields in wide bandgap compound semiconductors. He will provide insight to operation of devices under investigation by ONR funded PIs. Approach: Calculational theory and code developed over the last two decades will be used for theoretical modelling and prediction. Progress: A post.doc. RA, Dr. Ceyhun Butulay, joined Essex 1 January 1999. An exact solution of the Boltzmann equation for the low-field drift mobility in GaN associated with polar-optical-phonon scattering was obtained and published. Inclusion of electron-electron and acoustic-phonon scattering has now given us an upper limit to the bulk mobility. An extension to the 2D case has been made. A calculation of the low-field mobility in AlGaN will be presented at the Nitride Conference in Montpellier in July. Results of a study of piezoelectric scattering was presented at the Spring meeting of the MRS. The effect of Wannier-Stark quantization on the impact-ionization rate in bulk material has been published. Title: Low Energy Electron Microscopy Investigations of Fundamental Mechanisms in Group III Nitride Growth PI: Max Lagally THE BOARD OF REGENTS OF THE UNIVERSITY OF WISCONSIN Materials Science and Engineering Address: 750 University Avenue Madison, WI 53706 (608) 263-2078 Funding Agency: Office of Naval Research PR Number: 00PR00482-01 Award Number: N000149610323 Current End Date: 30-Sep-2002 Scientific Officer: Colin Wood Objective: To optimize the growth of GaN by application of Low Energy Electron microscopy real time to the epitaxial growth surface. Si quantum dots embedded in GaN films will be investigated for light emission and high power microwave applications relevant to the US Navy. Approach: Low-energy electron microscopy (LEEM) will be used to investigate the homoepitaxial growth of GaN on single crystal GaN substrates. The morphological aspects of the growth front will be studied as a function of growth parameters such as nitrogen pressure, deposition rate, temperature and substrate condition in order to determine quantitative thermodynamic and kinetic mechanisms. A novel atomic nitrogen source will be fabricated and installed in the LEEM. In this source a CO2 laser fires into the throat of a nozzle creating a nitrogen plasma. The plasma then expands and is neutralized by collisional recombination. Its composition is then frozen by the nozzle expansion. Progress: Low-energy electron microscopy (LEEM) has been used to investigate the homoepitaxial growth of GaN on single crystal GaN substrates. The morphological aspects of the growth front studied as a function of growth parameters such as nitrogen pressure, deposition rate, temperature and substrate condition have been used to determine quantitative thermodynamic and kinetic mechanisms. A novel atomic nitrogen source has been fabricated and installed in the LEEM. Using the new LEEM GaN chamber the PI has observed facetted growth of GaN on GaN/sapphire at low temperatures. PI has identified regions on LEO GaN suitable (because they have large, step-free regions) for investigating nucleation and initial growth. PI has tested the plasma source using oxygen, and has found that a significant hyperthermal component of O atoms is produced. PI has nearly completed the STM/GaN growth chamber and will grow GaN on Si(111), for purposes of integrating GaN/Si using multi-orientation SOI. PI has investigated patterned Si(001) and SOI in the LEEM, and has achieved large (~15m) step-free pedestals. Title: INTERFACIAL BONDING RESEARCH FOR COMPLIANT SUBSTRATES PI: David Miller THE PENNSYLVANIA STATE UNIVERSITY Science Center Address: 1049 Camino Dos Rios, P.O.Box 1085 Thousand Oaks, CA 91360 (805) 373-4275 Funding Agency: Office of Naval Research PR Number: 00PR00484-00 Award Number: N000149710951 Current End Date: 30-Jun-2000 Scientific Officer: Colin Wood Objective: To determine parameters of preparation of bonded substrates for molecular beam epitaxy of lattice mismatched electronic materials. Approach: Examine the effects of interfacial chemistry, gas, oxide and contami-nants, as well as surface finish and topography on the temperatures, conditions and results of bonded GaAs on Si. Progress: The PI has focused on two areas: relaxed epitaxial growth of InGaAs on a twist-bonded GaAs compliant substrates and GaAs compliant substrates bonded with intermediate SiO2 or indium oxide layers; and relaxed epitaxial growth of InGaAs on a compliant substrate fabricated by epitaxial growth of an AlAs/GaAs structure with the subsequent oxidation of the AlAs. They have developed methods to improve the cleanliness and smoothness of the surfaces of both types of compliant substrates for subsequent epitaxial growth and have successfully produced intact GaAs layers as thin as 30 nm on top of oxidized AlAs in stripes 100 micron wide. They have successfully grown GaAs epitaxially over these thin layers. So far, however, large areas of dislocation-free epitaxial material grown on these compliant substrates have not been achieved, in part because lattice-mismatched epitaxy still nucleates poorly on these surfaces.The postdoc previously supported by this program was hired by industry (QED, Inc., Bethlehem, PA) in February 1999 and a new postdoc with extensive material growth experience has been hired. Research focus has been shifted from thin GaAs on oxidized AlAs to twist-bonded materials and the use of bonded wafers using antimonide compliant layers. Careful characterization of InGaAs layers grown on thick GaAs substrates has been done as preparation for growth of InGaAs on these complaint substrates. Two papers were published last year reporting results from this project. Title: USE OF PIEZOELECTRIC CHARGE IN HEMT'S ON GaAs AND InP SUBSTRATES PI: Lester Eastman CORNELL UNIVERSITY School of Electrical Engineering Address: 120 Day Hall Ithaca, NY 14853 (607) 255-4369 Funding Agency: Office of Naval Research PR Number: 00PR00485-00 Award Number: N000149810161 Current End Date: 31-Dec-2000 Scientific Officer: Colin Wood Objective: To fabricate and investigate improvements of Field effect transistor operation and performance using piezo-electric fields in the C-direction of the crystals and thus avoid the need for dopant incorporation and control during epitaxial film growth. Approach: The PI will determine the magnitude of the Piezo electronic co-efficients in GaAs/AlInGaAs heterostructures in the (111) direction. Once determined FET devices will be designed, built and characterized, and the performance advantages evaluated. Progress: Initial experiments on oriented GaInAs on GaAs substrates have demonstrated the extent of Piezo-electric effect. Calculations are underway to determine the extent of spontaneous polarization to distinguish it from strain induced polarization effects. Attempts to achieve piezoelectrically-induced holes with (III)B GaAs substrates have been tried without success. The expected hole sheet density is well below 1 x 1012/cm2 and is masked by background donors in the buffer layer. The use of (III)B InP, to induce a 2DEG, where the density is expected to be 2-3 x 1012/cm2, is being studied. Lattice matched InGaAs and InAlAs have been achieved and growths of lattice-matched InGaAs covered with strained In1-yAlyAs will be made. Using a thin barrier of the latter, at the critical layer thickness, the 2 DEG density will be determined. Title: P-Type Doping in GaN PI: Fred Schubert THE TRUSTEES OF BOSTON UNIVERSITY College of Engineering Address: 44 Cummington Street Boston, MA 022152407 (617) 353-1910 Funding Agency: Office of Naval Research PR Number: 00PR00486-00 Award Number: N000149810194 Current End Date: 30-Nov-2000 Scientific Officer: Colin Wood Objective: To produce higher hole concentrations in GaN for much reduced resistance contacts, and lower parasitic series resistance in AMRFS related devices. Approach: PI will prepare oscilliatory compositional superlattices of Mg saturated GaN /InN films by molecular beam epitaxy. This will change the band structure thereby reducing the effective mass and thence the activation energy, and allowing low resistance contacts for AMRFS related devices. Progress: Instabilities in Hall measurements from samples of GaN grown on Sapphire have been discovered. A time dependant scan technique that leads to 3 orders of magnitude increased accuracy has been developed. Also discovered is that when using ethylene glycol as a solvent peroxide can be used and etchant such as phosphoric acid to define facets on c plane GaN on Sapphire. Mg-doped AlGaN/GaN superlattices are investigated in order to enhance the doping properties of GaN which suffers from low carrier activation due to an acceptor activation energy of 200 meV. Demonstrated that the activation energy of acceptors is reduced to 70 meV and 58 meV in AlGaN/GaN superlattices with 10% and 20% Al content, respectively. The free hole concentration of the superlattice with 20% Al content is 8 x 10^18 cm^-3 at 400 K. The doping properties improve with increasing Al content of the superlattices, in agreement with theoretical model. Title: Supplimental funding for N0001496-1-1008 PI: Thomas Myers WEST VIRGINIA UNIVERSITY RESEARCH CORPORATION ON BEHALF OF WEST VIRGINIA UNIVERSITY Department of Physics Address: P.O. Box 6315 Morgantown, WV 265066315 (304) 293-3422 Funding Agency: Office of Naval Research PR Number: 00PR00488-02 Award Number: N000149611008 Current End Date: 30-Sep-2002 Scientific Officer: Colin Wood Objective: This program seeks to determine and exploit the mechanism whereby hydrogen atoms enhance the stability of group III nitride thin films in vacuum, which enhances apparent growth rate during molecular beam epitaxy. Approach: Reflection electron diffraction and molecular desorption spectroscopy will be used as real-time probes of the surface stoichiometry, crysta-linity, and smoothness during thin film growth of the group III nitrides. MBE with elemental group III and nitrogen plasma sources will be employed. Progress: Atomic hydrogen stabilizes the growing GaN surface during molecular beam epitaxy (MBE), allowing higher temperatures necessary for high quality material. Study of defects affecting surface morphology suggest the majority of MBE growth results in a crystal polarity which enhances defect formation, indicating that growth initiation must be changed. The PI will continue to investigate growth kinetics of GaN, InN and InGaN (including the effect of atomic hydrogen) to understand growth processes and allow alloy growth at GaN-compatible temperatures. Title: GROWTH AND FABRICATION OF GaN-BASED HETEROJUNCTION BIPOLAR TRANSISTORS PI: April Brown GEORGIA TECH APPLIED RESEARCH CORPORATION GEORGIA INSTITUTE OF TECHNOLOGY School of Electrical and Computer Engineering Address: 212 Pettite Building Atlanta, GA 303320250 (404) 894-5161 Funding Agency: Office of Naval Research PR Number: 00PR00489-00 Award Number: N000149810209 Current End Date: 31-Dec-2000 Scientific Officer: Colin Wood Objective: To develop heterojunction bipolar transistors for high power microwave operation without active cooling. Approach: This program will utilize and exploit piezo-electric fields within heterojunction nitride semiconductor based bipolar transistor multilayer structures. These will be grown at GA Tech by MBE, and processed at U Illinois. Progress: This project has demonstrated: 1.) the first growth of a device quality nitride structure on lithium gallate, a low cost alternative substrate 2.) the elimination of the low temperature buffer normally required to nucleate the nitride films on heterogeneous substrates (this buffer is a source of defects that limits the device performance), 3.) the lowering of dislocation densities to the low 1e8 per cm2 range without the need for expensive multistep processes such as Lateral Epitaxial Overgrowth, and 4.) much improved AlGaN material quality (a critical part of the heterostructure) as evidenced by a 50% narrower X-ray diffraction width as compared to material grown on sapphire, HVPE GaN and silicon carbide. Have recently replaced Oxford rf plasma source with an EPI plasma source (July 99) and have realized increased growth rates (x3) and preliminary indications of increased p-type doping efficiency and control on sapphire and LGO substrates. Have designed heterostructures for achieving polarization (sponta-neous and piezoelectric) enhancements on cation- and anion-terminated growth faces. The achievement of a reproducible p-type doping is necessary to realize such enhancement. Theoretical studies of GaN/AlGaN HBT structures indicate that in the absence of piezoelectric effects and using a best estimate of the mobility and a free hole concentration of 1 cm2/V-s and 5.0 E18 respectively that the maximum value of fmax is about 3.5 GHz for a 0.075 micron wide base. Have also found that grading the heterojunction as opposed to using an abrupt heterojunction results in a 20% improvement in the integrated hole density when piezoelectric field effects are included. Title: Glasses and Fibers PI: Ishwar Aggarwal NAVAL RESEARCH LABORATORY Code 5603 Address: 4555 Overlook Avenue Washington, DC 20375 (202) 767-9316 Funding Agency: Office of Naval Research PR Number: 00PR00495-01 Award Number: N0001400WX20494 Current End Date: 30-Sep-2000 Scientific Officer: Yoon Park Objective: To increase the time-bandwidth product of present delay line technology and analog communication links by using fiber optics and related componentry. Approach: IR fibers and cable/AR coating will be developed. Purification and fiberization techniques will be developed to reduce the glass-cladd fiber loss to <0.3dB/m and increase the average fiber bend strength to >100kpsi. Ruggedized, vibration-proof cables which can tolerate the environmental conditions expected in harsh environment will be investigated. Progress: Glass cladd chalcogenide fibers have been developed, AR-coated and successfully used in the lab for IR jamming of missile seeker at Sanders. The IR cables are required for the Tri-Service ATIRCM Program for aircraft protection. In this system, the IR fiber is needed to connect the ATIRCM laser to the Jam Head, and thus replace the current Optical Coupler, which is cumbersome, heavy and difficult to align. Because of the importance of fiber for the ATIRCM program, the NRL IR fiber effort is currently being supported by the U.S. Army CECOM. NRL has a CRADA with Corning, Inc. for IR fiber amplifier development. Title: Mid-IR Type-II Quantum Well and Interband Cascade Lasers PI: Jerry Meyer NAVAL RESEARCH LABORATORY Optical Sciences Division Address: Code 5613 Washington, DC 203755338 (202) 767-3276 Funding Agency: Office of Naval Research PR Number: 00PR00496-00 Award Number: N0001400WX20321 Current End Date: 30-Sep-2000 Scientific Officer: Yoon Park Objective: To develop two new mid-IR sources, the type-II quantum well laser and the type-II interband cascade laser, which are projected to produce on the order of 1 W quasi-cw output power per facet at ambient or TE-cooler operating temperatures with near-diffraction-limited beam quality. Approach: Two new semiconductor mid-IR sources, the type-II quantum well laser (T2QWL) and the type-II interband cascade laser (T2ICL), which overcome the disadvantages of previous type-I and type-II approaches, and will consequently produce higher output powers at higher operating temperatures. A four-constituent (InAs-GaInSb-InAs-GaALSb) structure will be utilized. This structure is expected to be superior to the type-II superlattice(SL) because it displaces 2D dispersion relations for both electrons and holes. Progress: Electrically-pumped mid-IR lasers with type-II superlattice active region have yeilded record operating temperatures, pulsed output powers, and threshold current densities. The maximum power of 430 mW at 100 K is near the highest observed for interband diodes at 2.9 um, and the peak output of 100 mW at 200 K is higher than any previous result for > 2.9 um. The threshold current density was as low as 120 A/cm2 at 80 KK, and for all T>180 K the threshold current density values were the lowest ever reported for this wavelength range (e.g., 1.1 kA/cm2 at 200 K). Title: Optical Receivers PI: Ronald Esman NAVAL RESEARCH LABORATORY Code 5672 Address: 4555 Overlook Ave Washington, DC 203755320 (202) 767-9359 Funding Agency: Office of Naval Research PR Number: 00PR00497-00 Award Number: N0001400WR20052 Current End Date: 30-Sep-2000 Scientific Officer: Yoon Park Objective: To develop high-current photodetectors for use in state-of-the art photonic systems. This program emphasizes high current photodetectors and photodetectors interfaced with electronics(OEICs). Approach: Devices capable of detecting greater than 50 to 100 mA at 5 to 20 GHz and 100 to 200 mA below 5 GHz will be designed and fabricated. These devices will transition into various specific photonic systems which will perform more effectively than current electronic systems as well as providing new and advanced capabilities. Progress: Have achieved <4V Vpi at 20 GHz at 1.3 micron in etched ridge device. Tunable laser tuning range extended to 22 nm with the following paramters: 4.5 linewidth enhancement factor, 20 mA threshold, 0 dBm into the fiber, >45 dB SMSR. Longterm wavelength stability of SSG-DBR lasers was investigated indicating degradation leading to unacceptable mode hops (~5nm). Tuning algorithms to mitigate this degradation were developed and successfully tested. Long term verification of this concept is underway. Title: Optical Transmitters PI: Ronald Esman NAVAL RESEARCH LABORATORY Code 5672 Address: 4555 Overlook Ave Washington, DC 203755320 (202) 767-9359 Funding Agency: Office of Naval Research PR Number: 00PR00498-00 Award Number: N0001400WX20091 Current End Date: 30-Sep-2000 Scientific Officer: Yoon Park Objective: To increase the time-bandwidth product of present delay line technology and analog communication links by using fiber optics and related componentry. Approach: To increase the time-bandwidth product of delay lines the bandwidth of the components used in the delay line, namely; the laser diode transmitter and the p-i-n diodes photodetector are being increased. The development of the optical amplifier at 1.3 um and 1.5 um makes it necessary to develp components and systems at these wavelengths. Progress: Initial studies of Sampled Grating, Distributed Bragg Reflector (SGDBR) lasers indicate that they represent a very promising technology. They have a very good spurious mode suppression ratio (MSR>40dB), output powers on the order of 10 mW, and tuning ranges of up to 80 nm. Static characterization of the SGDBR devices shows relatively well-behaved CW operation. Approximately 10 mW CW power is available from this device. Have achieved <4V Vpi at 20 GHz at 1.3 micron in etched ridge device. Tunable laser tuning range extended to 22 nm with the following paramters: 4.5 linewidth enhancement factor, 20 mA threshold, 0 dBm into the fiber, >45 dB SMSR. Long term wavelength stability of SSG-DBR lasers was investigated indicating degradation leading to unacceptable mode hops (~5nm). Tuning algorithms to mitigate this degradation were developed and successfully tested. Long term verification of this concept is underway. Title: High Power 2.0 and 1.5um Fiber Source PI: Lew Goldberg NAVAL RESEARCH LABORATORY Department of Physics Address: Washington, DC 203755000 (202) 767-9079 Funding Agency: Office of Naval Research PR Number: 00PR00500-01 Award Number: N0001400WR20114 Current End Date: 30-Sep-2000 Scientific Officer: Yoon Park Objective: To develop high-power fiber amplifiers and lasers for use in remote sensing and laser countermeasure applications. The proposed research will result in high efficiency and compact fiber-based coherent optical sources suitable for use in 1.5 um eye-safe remote measurement systems such as micro-Doppler and LSADAR and as a 2.0 um pump for mid-IR optical parametric oscillator for laser countermeasure applications. Approach: The laser systems will rely on the use of optical fiber gain medium. The propagation loss of a silica fiber is approximately 10dB/km at 2.0 um. For typical fiber lengths of few tens of meters, the propagation loss in silica fiber at 2.0 um is therefore negligibly small. In the proposed 2.0 um fiber laser, a Tm doped fiber is pumped by a 1.5 um fiber laser constructed using a double cladding fiber containing a large Er/Yb co-doped core. The Er/Yb co-doped fiber laser is cladding-pumped by fiber-coupled 980 um laser diode bars. Progress: Tm doped fibers and crystals were characterized to determine their slope efficiency when pumped by 800 nm light. Based on these measurements a preliminary Tm doped fiber preform design was finalized and fabrication was initiated. The fiber preform was designed to have cladding ratio and doping concentration compatible with a double cladding fiber. Fiber amplifier based on double cladding fibers and side-pumping through a V-groove were demonstrated, generating up to 1.7 W at 1.5 um and 4 W at 1um. Record electrical-to-optical conversion efficiencies (42% for a Yb doped fiber amplifier) were demonstrated. Title: 3-Band IRFPA Technology PI: Joseph Omaggio NAVA | |