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Semiconductors
^ Photoluminescence Studies of Semiconductor Materials, Heterostructures, and Processing for Optoelectronic Devices
S. G. Bishop,* I. Adesida,* J. J. Coleman,* G. Papen, A. Mitofsky
University of Illinois

This research program applies photoluminescence (PL), photoluminescence excitation spectroscopy, time-resolved PL, and PL imaging to the characterization of defects and impurities in bulk and epitaxial semiconductor materials; the composition, doping, thickness, interfaces, and uniformity of semiconductor nanostructures; rare earth-doped semiconducting glasses; and rare earth implanted GaN for near- and mid-IR sources.

^ Bio-Optoelectronics Sensor Systems Center
K. Y. Cheng,* S. L. Chuang,* M. Feng,* N. Holonyak, Jr.,* K. C. Hsieh,* Z. P. Liang*
Defense Advanced Research Projects Agency, MDA 972-00-1-0020

The goal of this center program is the development of integrated optoelectronic technologies, including materials, devices, integrated interferometers, optical microelectromechanical system (MEMS) spectrometers, and heterogeneous integration, that are critical to the realization of integrated and reconfigurable biological and biochemical sensor systems. Microspectrometer and interferometer-waveguide based optoelectronic biosensor systems will be developed to improve the size, cost, sensitivity, and signature resolution of the fieldable sensors for detecting biological and chemical entities in the environment in real-time through on-chip optical measurements.

^ GaAs-based Metal-Oxide-Semiconductor Structures
K. Y. Cheng,* K. C. Hsieh*
Bell Laboratories; Lucent Technologies

The goal of this research program is to develop oxide deposition techniques for the fabrication of GaAs-based metal-oxide-semiconductor field effect transistors (MOSFETs). Various oxides including SiO2, Al2O3, Ga2O3, and Gd3Ga5O12 are deposited on GaAs in an ultrahigh vacuum system at Bell Laboratories to form MOS structures. Researchers will characterize their structural, optical, and chemical properties through transmission electron microscopy, photoluminescence spectroscopy, and Auger electron spectroscopy, respectively, to improve the oxide deposition process.

^ Stable Wavelength Strained Quantum Wire Lasers
K. Y. Cheng,* Y. C. Chang,*
National Science Foundation, ECS 9617153

The goals of this research are to develop technologies in the fields of epitaxial growth of strained quantum wire (QWR) structures by molecular beam epitaxy (MBE), multiaxial strain engineering, and computer modeling of low-dimensional strained structures based on efficient band-structure models to make possible the fabrication of wavelength stable semiconductor lasers for optical fiber communication and information applications. Specifically, researchers will fabricate wavelength stable 1.55 μm GaxIn1-xAs/InP lasers that employ strained QWR active regions formed in situ by the strain-induced lateral-layer ordering (SILO) process during MBE growth.

^ VCSEL and Smart Pixel Research for VLSI Photonic Systems
K. Y. Cheng,* N. Holonyak, Jr.,* M. Feng,* K. C. Hsieh,*
Defense Advanced Research Projects Agency, DAAG55-98-1-0303

The purpose of this research is to develop technology related to VLSI photonic systems. The scope of the program ranges from basic materials research, to the fabrication of large-scale integrated circuits, to advanced technologies for the integration of systems in heterogeneous materials. Goals of the project include the design, growth, fabrication, and testing of III-V semiconductor vertical cavity surface-emitting lasers; the development of smart pixels, circuits for the detection of optical signals, intelligent routing of the information, and re-emission of optical signals; and the development of techniques for the integration of heterogeneous materials.

^ Nanometer-Scale Vertical Cavity Lasers
K. D. Choquette*
University of Illinois

The development of ultracompact photonic light sources will be important for next generation applications in data communication, optical interconnects, and biological sensing. This program will develop extremely small volume vertical cavity surface emitting lasers (VCSELs) by incorporating photonic band gap structures within the laser active region. The objective of implementing strong transverse optical confinement is to establish single optical mode cavities with significantly reduced threshold operation. In addition, the artificially structured photonic gap may enable novel coupling schemes for coherent two-dimensional VCSEL arrays.

^ Spatially Multiplexed VCSEL/Receiver Optical Interconnect
Kent D. Choquette*
University of Illinois

For high data rate transmission, spatial multiplexing of many optical channels will enable multi-terabit/sec optical interconnects. The foundation of such a system will rely on two-dimensional arrays of transmitters and receivers, with a means of interconnection. This program will establish a spatially multiplexed interconnect testbed and characterize the performance of the system components. Arrays of 8x8 individually addressable vertical cavity lasers (VCSELs) with driver chips and matching arrays of metal/semiconductor/metal photodetectors monolithically integrated with MESFET amplifiers will be examined. A guided wave optical interconnect will be pursued utilizing an optical fiber image guide.

^ Materials Research for High-Performance Optoelectronic Devices Employing III-V Compound Semiconductor Native Oxide Layers
N. Holonyak, Jr.,* J. Miller
National Science Foundation, DMR-9612283; University of Texas-Austin

The primary thrust of this program is the growth and characterization of heteroepitaxial materials employing native oxide layers. A variety of optoelectronic structures are being grown by MOCVD including AlGaAs/GaAs, InAlP/GaAs, and InAlP/InGaP double heterostructures. Currently under investigation are the minority carrier lifetime in the active regions, the interface recombination velocity between the active and oxide regions, and the effect of various oxidation conditions upon interface abruptness and impurity distributions. The results of this research will enable further advances in VCSEL (laser), field-effect transistor (MOSFET), and other technologies utilizing native oxide layers.

^ CAD Design Tools for Millimeter Wave Wireless Communication Microsystems
C. Liu,* M. Feng, S. Kang, E. Michielssen, J. Schutt-Aine
Defense Advanced Research Projects Agency, Composite-CAD Program, F30602-97-0328

A mixed technology computer-aided design system is being developed for the cost effective design of wireless communication modules that will ultimately enable networked distributed MEMS. The module, operating at millimeter wave frequencies, will allow direct interface between MEMS transducers and the free-space electromagnetic radiation. MEMS components offer unique advantages for RF circuits. As an example, micromechanical switches exhibit lower insertion loss and higher isolation compared with conventional electronics switching components. MEMS fabrication technology for silicon as well as composed semiconductor materials are being studied, in order to realize mechanical RF switches as well as high-gain antennas to validate results of the E-M simulation.

^ Efficient Computational Prototyping of Mixed Technology Microfluidic Components and Systems
C. Liu*
Defense Advanced Research Projects Agency

The objective is to develop microfluid components (including pumps and valves), materials (including polymeric MEMS and biodegradable materials), and applications (including drug delivery systems). Microfluid circuits are on the scale of micrometer to millimeter; they are used to transport biological and chemical materials.

^ Integrated Biomimetic Sensors Using Artificial Hair Cells
C. Liu*
National Aeronautics and Space Administration

Biological systems provide essential inspiration for integrated sensors development. This work is funded by NASA and is aimed at developing modular sensor building blocks to drastically simplify the sensor development process for future space applications.

^ Integrated Capillary Microelectrode Arrays for Studies of Olfactory Response Patterns in the Insect Brain
C. Liu*
Defense Advanced Research Projects Agency Controlled Biological Systems Program

This project aims to develop the first arrayed capillary microelectrodes using integrated microfabrication technology and to demonstrate the enhanced capabilities for monitoring neurological behavior of insect olfactory systems.

^ Mechanically Conformal and Electronically Reconfigurable Aperture (RECAP) Using Low-Voltage MEMS and Flexible Membrane for Space-based Radar Applications
C. Liu*
Defense Advanced Research Projects Agency

The objective is to develop micromachined antennas with reconfigurible wavelength and directionality using micromachined switches. We are currently developing micromachining processes based on polymeric materials to realize three-dimensional RF MEMS.

^ Surface Engineering for Compliant Epitaxy
K. C. Hsieh,* K. Y. Cheng,* I. Adesida
Defense Advanced Research Projects Agency, F49620-98-1-0496

The goal of this research is to realize dislocation-free and stress-relaxed lattice mismatched epitaxy growth of different compound semiconductors on various substrates across the whole wafer or on selected areas for device integration applications. Our immediate goals include fundamental understanding of the growth conditions related to the formation of strained-modulated and defect-absorbing templates and the development of techniques to fully control the formation of strain-absorbing and deformable growth templates with an emphasis on processing simplicity and system integrability. InP-based optoelectronic and microwave devices will be integrated selectively on surface-engineered GaAs substrates.

^ Controlled Coupling of Donor Atom Wavefunctions in Silicon
J. Tucker, J. Kline, T. C. Shen (Utah State Univ.)
U.S. Army Research Office DAAD 19-00-1-0407

The goal of this project is to selectively place PH3 molecules onto the hydrogen-terminated silicon surface via STM lithography and overgrow them into the crystal as phosphorous donors. If successful, this work could provide a means for constructing quantum computers based on control of ground-state wavefunctions on individual P-atom donors. Other potential applications include single-charge electronics, cellular automata, and nanometer-scale field-effect transistors. Reproducible characteristics are made possible by the large ~5nm Bohr diameter for individual donor bound states, so that coupling between nearest neighbors will be accurately defined if redistribution is limited to ~1nm or less during ultra-low-temperature overgrowth.

^ Wavefunction Engineering of Individual Donors for Si-Based Quantum Computers
J. Tucker,* M. Feng, Y. C. Chang, T. C. Shen (Utah State Univ.), R. R. Du (Univ. of Utah)
U.S. Army Research Office, 42257-PH-QC

The goal of this multi-investigator program is to develop the basic fabrication and measurement technologies needed to implement a silicon-based quantum computer. To do this, researchers must place individual phosphorous donors into the silicon lattice with atomic precision, establish electrical control over wavefunction overlap between donor-pairs, and successfully detect spin states of the resulting two-electron system by measuring the presence or absence of electronically-induced polarization. The research team does not propose working quantum logic gates within this three-year project. If successful, however, that goal will be undertaken in a follow-up program that incorporates SiGe overgrowth and patterning of individual top-gates for each P-atom donor.


Summary of Engineering Research