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7 April 1999 Avalanche photodetector in the GaSb/AlSb/InAs material system by molecular beam epitaxy
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GaSb/AlSb/InAs is an attractive system for making low noise avalanche photodetectors (APD) due to possible resonant enhancement of hole impact ionization in AlxGa1-xSb and potential enhancement of electron impact ionization in GaSb/AlSb superlattices. We have employed molecular beam epitaxy (MBE) to fabricate device structures so that these effects could be further explored. The devices were grown on GaSb substrates and incorporated a p-n+ one sided abrupt junction. The p- multiplication region consisted of either bulk Al0.04Ga0.96Sb or 10 periods of alternating, 300 angstrom thick GaSb and AlSb layers. A short period, selectively doped InAs/AlSb superlattice was used as the n+ layer. Dark current suppression in these devices was found to be largely dependent on the InAs/AlSb superlattice configuration and the resulting band offset at the p-n+ heterojunction. Notably, for devices with a 0.6 micrometer Al0.04Ga0.96Sb multiplication region and an optimized InAs/AlSb superlattice, an avalanche break down voltage of 13 V was observed. The dark current density for this device was 6 A/cm2 at a multiplication factor of 10. Devices with GaSb/AlSb superlattice multiplication regions exhibited a higher breakdown voltage (18.5 V) and a lower dark current density (0.4 A/cm2) at comparable gain. Impact ionization rates in Al0.04Ga0.96Sb were studied by using 781 nm and 1645 nm laser light. The results were consistent with enhancement of hole impact ionization in Al0.04Ga0.96Sb.
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Xiao-Chang Cheng and Thomas C. McGill Jr. "Avalanche photodetector in the GaSb/AlSb/InAs material system by molecular beam epitaxy", Proc. SPIE 3629, Photodetectors: Materials and Devices IV, (7 April 1999);

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