Midwave infrared type-II InAs∕GaSb superlattice detectors with mixed interfaces

Abstract

We report the growth and fabrication of midwave infrared InAs∕GaSb strain layer superlattice (SLS) detectors. Growth of alternate interfaces leads to a reduced strain between the GaSb buffer and SLS (Δa‖∕a=−5×10−4), enabling the growth of active regions up to 3μm (625 periods). The structural, optical, and electrical properties of the active region were characterized using x-ray crystallography and photoluminescence, respectively. p-i-n detectors were grown using 625 periods of 8 ML (monolayer) InAs∕8 ML GaSb as the active region. The λcutoff for the detectors was 4.6μm with a conversion efficiency of 32% at Vb=−0.2V. Detectivity was obtained using noise power spectral density measurements under 300K 2π field of view illumination and was equal to 5.2×1010 and 3×1010cmHz1∕2∕W (Vb=−0.02V, T=80K) in the white noise and 1∕f noise limit (at 50Hz).