Temperature-dependent minority carrier lifetime in InAsSb nBn detectors on alternative substrates

Abstract

The 6.1 A family of Sb-based III-V materials and heterostructures is a promising candidate for infrared (IR) detector applications. For the realization of low-cost, large-format IR photodetector arrays these materials must be grown on larger diameter substrates. For this purpose, GaAs substrates, with appropriate metamorphic buffer structures, have shown to be a promising alternative. Moreover, other platforms, such as Ge-on-Si (Ge/Si) and Ge-on-insulator-on-Si (GeOI/Si) virtual substrates, enable direct integration of the III-V devices with Si microelectronics read-out and processing architectures. In this paper, we investigate the structural and optoelectronic quality of mid-wavelength infrared InAsSb nBn photodetectors with a room temperature 50% cut-off wavelength of 4.5 μm grown on multiple substrates, including GaSb, GaAs, and Ge/Si. Material quality was examined using non-contact, non-destructive electron channeling contrast imaging (ECCI) in a scanning electron microscope for high-accuracy threading dislocation density (TDD) measurement and time-resolved microwave reflectance (TMR) spectroscopy for minority carrier lifetime (τmc) measurement. The combination of these two techniques enables a direct correlation between TDD and τmc. Our preliminary data indicate that higher TDD results in a reduced lifetime, similar to observations in III-V materials and HgCdTe IR materials. Here we present our analysis of equivalent nBn structures grown on GaSb, GaAs, and Ge/Si. The results of τmc indicate that the sample on GaSb and GaAs have the longest and the shortest lifetime, respectively, for temperatures above 70 K. Combining lifetime characterization with the TDD analysis from ECCI enables the assessment of metamorphic detectors on alternate substrates as a platform for large-format focal plane arrays.