A5027354097- Chalcogenide Semiconductor Thin Films
- Advanced Semiconductor Detectors and Materials
- Quantum Dots Synthesis And Properties
- Semiconductor Quantum Structures and Devices
- solar cell performance optimization
- Advanced Electron Microscopy Techniques and Applications
- Thermography and Photoacoustic Techniques
- Nanowire Synthesis and Applications
- Perovskite Materials and Applications
- Gas Sensing Nanomaterials and Sensors
- CCD and CMOS Imaging Sensors
- Ga2O3 and related materials
- Electron and X-Ray Spectroscopy Techniques
- ZnO doping and properties
- Integrated Circuits and Semiconductor Failure Analysis
Arizona State University
2009-2020
Photonics (United States)
2014
University at Buffalo, State University of New York
2009
CdTe/MgCdTe double heterostructures (DHs) are grown on InSb substrates using molecular beam epitaxy and reveal strong photoluminescence with over the intensity of a GaAs/AlGaAs DH an identical layer structure design GaAs. Time-resolved gives Shockley-Read-Hall recombination lifetime 86 ns, which is more than one order magnitude longer that typical polycrystalline CdTe films. These findings indicate monocrystalline DHs effectively reduce surface recombination, have limited nonradiative...
The bulk Shockley-Read-Hall carrier lifetime of CdTe and interface recombination velocity at the CdTe/Mg0.24Cd0.76Te heterointerface are estimated to be around 0.5 μs (4.7 ± 0.4) × 102 cm/s, respectively, using time-resolved photoluminescence (PL) measurements. Four CdTe/MgCdTe double heterostructures (DHs) with varying layer thicknesses were grown on nearly lattice-matched InSb (001) substrates molecular beam epitaxy. longest 179 ns is observed in DH a 2 μm thick layer. It also shown that...
We compare three representative high performance PV materials: halide perovskite MAPbI3, CdTe, and GaAs, in terms of photoluminescence (PL) efficiency, PL lineshape, carrier diffusion, surface recombination passivation, over multiple orders photo-excitation density or appropriate for different applications. An analytic model is used to describe the excitation dependence intensity extract internal efficiency pertinent parameters. A imaging technique obtain diffusion length without using a...
This Letter reports the optical properties of CdTe/MgCdTe double heterostructures grown by molecular beam epitaxy. Low-temperature photoluminescence shows strong band-to-band emission and very weak defect related peaks, indicating low densities. The measured Shockley–Read–Hall lifetimes range from 57 to 86 ns at room temperature for samples under different conditions. material radiative recombination coefficient B in rate defined as R=AΔn+(1−γ)BΔn2+CΔn3 [Wang et al., Phys. Status Solidi 244,...
A modeling study has been undertaken to compare CdTe versus GaAs solar cells in order explore and forecast the possible evolution of cell performance while using as a benchmark. complementary experimental comparison two almost identical MgCdTe/CdTe/MgCdTe AlGaAs/GaAs/AlGaAs double-heterostructure (DH) samples grown by MBE guided modeling. Both DH give strong photoluminescence at room temperature (RT) time-resolved measurements reveal 50 ns carrier lifetime RT for sample. The results based on...
A two-terminal multicolor photodetector that is most advantageous for greater than two bands proposed. This design particularly significant focal plane arrays as it maximizes the fill factor and simplifies readout integrated circuits. Individual color detection realized with appropriate optical biasing. concept demonstrated experimentally using a three-color biasing light emitting diodes. The measured linear dynamic range four orders of magnitude, making practical device broad applications.
A CdZnTe/MgCdTe double-heterostructure (DH) consisting of a 3 μm thick Cd0.9946Zn0.0054Te middle layer that is lattice-matched to an InSb substrate has been grown using molecular beam epitaxy. long carrier lifetime 3.4 × 102 ns demonstrated at room temperature, which approximately three times as CdTe/MgCdTe DH with identical thickness. This substantial improvement due the reduction in misfit dislocation density CdZnTe alloy. In contrast, CdTe on exhibits strain relaxation ∼30%, leads wider...
Microscopic defects can degrade the spatially averaged carrier density---and so performance---of solar cells and light emitters. The authors devise a technique to measure lifetime at high spatial temporal resolution, use it study cadmium telluride, one of most technologically important materials for thin-film cells. They find that depletion near certain profoundly influences effective extent those defects.
The mean inner potential (MIP) and inelastic free path (IMFP) of undoped ZnTe are determined using a combination off-axis electron holography convergent beam diffraction. MIP is measured to be 13.7±0.6 V, agreeing with previously reported simulations, the IMFP at 200 keV 46±2 nm for collection angle 0.75 mrad. Dynamical effects affecting holographic phase imaging as function incident direction several common semiconductors systematically studied compared Bloch wave simulations. These...
Effects of nitrogen doping ZnO (ZnO:N) during deposition and after postdeposition annealing have been studied by optical techniques, electronic properties, the application to metal-semiconductor-metal photodetectors (MSM-PDs). Films ZnO, doped rf sputtering, show larger grain size, narrower full width at half maximum, band gap emission shift in photoluminescence, higher conductivity. Postannealing has using tube furnace rapid thermal nitrogen. These methods not only reconstruct lattice...
Abstract ZnTe PN homojunctions are fabricated using thermal diffusion of Al into a film grown on lattice‐matched GaSb substrates by molecular beam epitaxy. Rectifying J‐V characteristics and the photovoltaic effect observed which suggests that n‐type has been successfully achieved. The reverse bias breakdown voltage is found to be dependent annealing condition acceptor concentration, trend agrees with junction theory. Secondary ion mass spectrometer depth profiles show Zn Te out‐diffuse...
Dark line defects arising from dislocations in epitaxial CdTe films are known to strongly limit the overall performance of optoelectronic devices. However, their effect on carrier diffusion length and lifetime material immediately surrounding is not well quantified. We apply a photoluminescence imaging technique directly measure these parameters CdTe/MgCdTe double heterostructure. Radiative recombination reduced by up 85% within 5 µm dislocation. Additionally, decrease ∼50 ∼80%, respectively.
Optical and structural properties of InAs/InAsSb type-II superlattices (T2SL) their feasibility for mid- longwavelength infrared (MWIR LWIR) photodetector applications are investigated. The T2SL structures with a broad bandgap range covering 4 μm to 12 grown by molecular beam epitaxy characterized highresolution x-ray diffraction photoluminescence (PL) spectroscopy. All the samples have excellent strong PL signal intensities same order magnitude, indicating that non-radiative recombination...
Confocal photoluminescence is shown to be a powerful tool for analyzing defect structure in epitaxial CdTe appropriate photovoltaic applications. Non-radiative defects such as dislocations are easily mapped and quantified. Photoluminescence intensity measurements valuable quantifying interface state density. Very low dislocation density twin content can achieved CdTe, densities result from using CdMgTe barriers.
Confocal photoluminescence scans of monocrystalline CdTe/MgCdTe double heterostructures epitaxially grown on lattice-matched InSb substrates reveal very low twin defect density, below 1 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</sup> cm xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> . Room-temperature Shockley-Read-Hall (SRH) lifetimes these samples are determined in the range 35 ns to 86 using time-resolved (TRPL)...
Abstract Aluminum doped ZnTe epitaxial layers have been grown on GaSb substrates by molecular beam epitaxy under different Te/Zn flux ratios, while the ratio is varied keeping Te constant and changing Zn flux. The ∼0.9 leads to narrowest full width at half maximum of x‐ray diffraction rocking curve. Indium deposition applied improve contact conductivity, characterized current‐voltage measurements. effect annealing in forming gas (5% H 2 + 95% Ar) has studied secondary ion mass spectrometry...
This paper reports recent experimental work on single junction II-VI semiconductor heterostructure solar cells consisting of n-type CdSe and p-type ZnTe grown by molecular beam epitaxy GaSb substrates. The structural crystalline properties are characterized using high-resolution X-ray diffraction measurements. current-voltage measurements reveal expected diode-like rectifying characteristics with considerable photo current strong photovoltaic effects under light illumination. These results...