posted 06-07-2002 02:20 PM            

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.
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posted 06-07-2002 02:21 PM            

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