20 research outputs found
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Analysis of Carrier Recombination Processes in 0.6 eV InGaAs Epitaxial Materials for Thermophotovoltaic Devices
Minority carrier lifetime was measured by time-resolved photoluminescence (TRPL) method in sets of p-type and n-type InGaAs double heterostructures (DH) moderately doped with Zn and Te, respectively. Contributions of the radiative and non-radiative recombination terms were separated by fitting experimental data to temperature dependences of the radiative term. The latter was modeled with measured fundamental absorption spectrum and the temperature dependence of the photon recycling effect was taken into account. Different temperature dependences of radiative terms for electron and hole materials were obtained. It was concluded that in 0.6 eV Te-doped InGaAs structures the radiative recombination controls the hole lifetime at liquid nitrogen temperatures, while Auger recombination dominates at room and above room temperatures. In similar 0.6 eV InGaAs with Zn-doped active regions Shockley-Read-Hall (SRH) recombination was found dominant in a wide temperature range from liquid nitrogen to above-room temperatures. Rapid decrease of electron lifetime with decrease of excess carrier concentration was observed and attributed to recombination through partially-ionized deep donor centers. The obtained data allows for more adequate modeling of the performance and design optimization of narrow-gap photonic devices based on InGaAs Indium-rich compounds
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Effect of Growth Interruption on Surface Recombination Velocity in GaInAsSb/AlGaAsSb Heterostructures Grown by Organometallic Vapor Phase Epitaxy
The effects of growth interruption on the quality of GaInAsSb/AlGaAsSb heterostructures grown by organometallic vapor phase epitaxy are reported. In-situ reflectance monitoring and ex-situ characterization by high-resolution x-ray diffraction, 4K photoluminescence (PL), and time-resolved PL indicate that GaInAsSb is extremely sensitive to growth interruption time as well as the ambient atmosphere during interruption. By optimizing the interruption sequence, surface recombination velocity as low as 20 cm/s was achieved for GaInAsSb/AlGaAsSb double heterostructures
Analysis of Recombination Processes in 0.5-0.6 eV Epitaxial GaInAsSb Lattice-matched to GaSb
Abstract. This work summarizes recent data on minority carrier lifetime in n-and p-type double heterostructures (DHs) of 0.5-0.6 eV GaInAsSb confined with GaSb and AlGaAsSb cap layers. Recombination times were measured by time-resolved photoluminescence (TRPL) and by optical frequency response (OFR) to sinusoidal excitation. It was shown that one of the mechanisms responsible for interface recombination in GaSb/GaInAsSb/GaSb DHs is thermionic emission of carriers over the heterobarrier. Considerable improvement of carrier confinement was obtained with 1 eV AlGaAsSb cap layers. Optimization of the epitaxial growth resulted in a recombination velocity at GaInAsSb/AlGaAsSb interface as low as 30 cm/s
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Wafer Bonding and Epitaxial Transfer of GaSb-based Epitaxy to GaAs for Monolithic Interconnection of Thermophotovoltaic Devices
GaInAsSb/AlGaAsSb/InAsSb/GaSb epitaxial layers were bonded to semi-insulating GaAs handle wafers with SiO{sub x}/Ti/Au as the adhesion layer for monolithic interconnection of thermophotovoltaic (TPV) devices. Epitaxial transfer was completed by removal of the GaSb substrate, GaSb buffer, and InAsSb etch-stop layer by selective chemical etching. The SiO{sub x}/TiAu provides not only electrical isolation, but also high reflectivity and is used as an internal back-surface reflector. Characterization of wafer-bonded epitaxy by high-resolution x-ray diffraction and time-decay photoluminescence indicates minimal residual stress and enhancement in optical quality. 0.54-eV GaInAsSb cells were fabricated and monolithically interconnected in series. A 10-junction device exhibited linear voltage building with an open-circuit voltage of 1.8 V
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Lattice-Matched GaInAsSb/A1GaAsSb/GaSb Materials for Thermophotovoltaic Devices
High-performance GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic (TPV) devices with quantum efficiency and fill factor near theoretical limits and open-circuit voltage within about 15% of the limit can be routinely fabricated. To achieve further improvements in TPV device performance, detailed materials studies of GaInAsSb epitaxial growth, the microstructure, and minority carrier lifetime, along with device structure considerations are reported. This paper discusses the materials and device issues, and their implications on TPV device performance. In addition, improvements in TPV performance with integrated distributed Bragg reflectors and back-surface reflectors are discussed
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Measurement of the Auger Recombination Rate in p-type 0.54-eV GaInAsSb by Time-Resolved Photoluminescence
Auger recombination in p-type GaSb, InAs and their alloys is enhanced due to the proximity of the bandgap energy and the energy separation to the spin split-off valence band. This can affect the device performance even at moderate doping concentration. They report electron lifetime measurements in a p-type 0.54-eV GaInAsSb alloy, commonly used in a variety of infrared devices. They have studied a series of double-capped heterostructures with varied thicknesses and doping levels, grown by organometallic vapor phase epitaxy on GaSb substrates. The Auger coefficient value of 2.3 x 10{sup -28} cm{sup 6}/s is determined by analyzing the photoluminescence decay constants with a systematic separation of different recombination mechanisms
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Effects of Radiative Recombination and Photon Recycling on Minority Carrier Lifetime in Epitaxial GaINAsSb Lattice-matched to GaSb
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Analysis of Recombination Processes in 0.5 - 0.6eV Epitaxial GaInAsSb Lattice-Matched to GaSb
After a brief introduction and work motivation, static and dynamic methods for minority carrier lifetime measurements will be compared. Data on recombination velocity at heterointerfaces for both p-type and n-type quaternaries will be summarized. Radiative recombination and effect of photon recycling will be considered in detail