Development of Bulk InAsSb Alloys and Barrier Heterostructures for Long-Wave Infrared Detectors

Bulk unrelaxed InAsSb alloys with Sb compositions up to 65% were grown on compositionally graded GaInSb and AlInSb buffers on GaSb substrates by molecular beam epitaxy. The minimum energy gap for these materials at T = 77 K was estimated to be 90 meV. Benchmark material parameters were measured for barrier photodetector heterostructures with 1-mu m-thick InAs0.6Sb0.4 absorbers. A minority hole lifetime of 185 ns and a diffusion length of 9 mu m at T = 77 K were determined from the transient response of barrier heterostructures. The data imply a hole mobility of 10(3) cm(2)/Vs, which was confirmed with frequency response measurements. A 100-mu m square mesa contact nBn heterostructure demonstrated a -3 dB frequency response bandwidth of 50 MHz.