Metamorphic Buffer Layer Growth for Bulk InAs(x)Sb(1-x) LWIR Detectors

Bulk InAs(x)Sb(1-x) is an infrared detector material that promises higher quantum efficiency than antimony-based superlattices in the longwave infrared (LWIR). This is due to the longer diffusion length of minority carrier holes in the bulk than in superlattices where they are localized. No native substrate exists for lattice-matched growth of InAs(x)Sb(1-x) material with LWIR bandgaps. So a key challenge is finding a suitable buffer that will minimize the crystal dislocation defects that will inevitably result from lattice-mismatched growth of InAs(x)Sb(1-x) on a substrate such as GaSb or GaAs. Such defects provide leakage paths and increase dark current. They also reduce minority carrier lifetime which reduces diffusion length and therefore quantum efficiency. Eliminating these defects is key to device performance. One solution is a suitable metamorphic buffer layer that filters out crystal dislocations and provides a template for the defect-free growth of the subsequent device layers. In this Phase I, a QmagiQ-led team of device, material growth and material analysis experts will try and develop such a buffer with the goal of achieving high-operability focal plane arrays of bulk InAs(x)Sb(1-x). Phase II will more deeply explore defect reduction schemes for material compositions that have the smallest energy bandgaps.