Research
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Theory and Modeling Group: The Center’s device theory and modeling group is headed by Prof. Aram Karakashian.
Libraries of canned and student-generated software are maintained in order to support center activities. The Center’s approach to thesis work requires all students to work on both theory and experiment. The group’s current focus is on terahertz lasers, high-speed photodetectors and micro-electrical-mechanical membranes.
Experimental Group: The Experimental Group is headed by Prof. William Goodhue.
Current interests include: III-V MBE Technology, particularly GaSb and other 0.61 nm, III-V materials, particularly as they apply to avalanche photo diode technology, Surface States in Quantum Wells, Ohmic Contacts to Antimonide based semiconductors, Integrated Waveguide Optics, Optical-MEMS sensors, Frequency Selective Materials, Photonic Crystals and metamaterials, Surface-States and gas cluster ion beam smoothing of GaSb, Point Defects in Semiconductors, Diode, Quantum Cascade, and SHOC Lasers, Semiconductor Etching Techniques, and Fabrication Techniques.
A few of our current research projects include:
Developing "epi-ready" GaSb Substrates for MBE Overgrowth
InSb Based Homoepitaxial structures
Development of Novel Device Assemblies and Techniques for Improving Adaptive Optics Imaging Systems
Left-Handed Meta-Materials the Visible
Measurement of Impact Ionization Coefficients in AlGaAsSb for varying Al concentrations
Developing “epi-ready” GaSb Substrates for MBE Overgrowth
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AlGaSb marker Transition free |
This project dealt with the development of “epi-ready” chemical mechanical polished GaSb substrates for epitaxial grwoth using different ion beam processing methods. Gas cluster ion beam processing (GCIB) of GaSb substrates was shown to be effective in producing smooth and defect free surfaces with a thin and easily desorbable oxide layer for MBE overgrowth and explored in detail by K. Krishnaswami. In-house Br-IBAE processed surfaces used for the overgrowth resulted in transition free interfaces by XTEM with much rougher episurfaces (AFM). Developed in conjunction, Br-GCIB processed GaSb surfaces used for the MBE overgrowth resulted in transition free interfaces with uniform step-terrace formation, thus making it as an ideal candidate for producing “epi-ready” GaSb substrates. Click here for detailed description.
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InSb Based Homoepitaxial structures:
Chemical mechanical polished and GCIB processed InSb substrates were tested for successful homoepitaxial growth for applications involving focal plane array detectors. By choosing proper Sb to Influx ratios and a substrate temperature, high quality InSb homoepitaxial structures were grown as confirmed by XTEM for interface defects and for surface morphology by AFM.
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Development of Novel Device Assemblies and Techniques for Improving Adaptive Optics Imaging Systems
The goal of this research is to develop novel Adaptive Optics (AO) amplitude and phase correction image processing assemblies and techniques. For the first time ever, Dynamic Range Compression technique is proposed as a deconvolution method for image restoration with noise reduction. All optically addressed deformable mirror Micro-Electro-Mechanical-System (MEMS) devices with this capability has been proposed, designed, fabricated, and modeled. Click here for detailed description.
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Design, fabrication and FEM modeling of an Optical-MEMS vibration sensor | |
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In this work a micro-cantilever optical-MEMS sensor based on AlGaAs system is designed and modeled. The device consists of two micro-cantilever beams perfectly aligned with the free ends separated by approximately 200 nm up to 2000 nm. The beams consisting of dielectric waveguides are designed for single mode propagation of 785 nm or longer wavelengths. When the device is externally driven with a piezo chip, the misalignment of the beams at resonance causes coupling loss from one beam to the other, resulting in the change in transmission power measured at the output beam. This effect can be utilized for vibration sensing, or simply optical modulation.
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After five years of experience in growing InAs/GaAs quantum dot structures by Molecular Beam Epitaxy (MBE), POD has proposed to design and fabricate terahertz frequency quantum dot photodetectors based on III-V semiconductor materials. THz radiation boosts the electron from the lower level to the upper level of the quantum dots where it thermalizes into the conduction band of the barrier. These quantum dot structures will be formed by etching stacked quantum wells, followed by a planarized regrowth to passivate the dot sidewalls. After the overgrowth of quantum dot epi-structures, the quantum dot detectors will be fabricated using standard photolithography and wet-etching techniques. In the meantime, photoluminescence (PL) and atomic force microscopy (AFM) measurements will be performed to characterize quantum dots. Spectra response,responsivity and detectivity will also be measured to characterize the performance of quantum dot detectors.
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Left-Handed Meta-Materials in the Visible
The purpose of this project is to design and fabricate a LHM (left handed meta-material) in the visible and experimentally verify its effective index of refraction. In this way we also hope to be able find ways to reduce the absorption effects encountered by the experimentalists in the frequency range where the meta-material becomes LHM. Also, we hope to find useful applications of these materials’ strange properties in the visible Click here for detailed description.
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Measurement of Impact Ionization Coefficients in AlGaAsSb for varying Al concentrations
AlGaAsSb can be grown lattice matched to GaSb and used as a multiplication layer in IR photodiodes. Knowledge of the Impact Ionization Coefficients will allow for more accurate device modeling and optimization of the multiplication region. A large difference in ionization coefficients for electrons and holes results in superior noise and bandwidth performance. The aim is to find which Al concentration yields the largest ratio of the >electron and hole ionization coefficients.