Passivation of Bulk and Surface Defects in III-V Bismuth-based Detectors

Infrared imaging systems are of critical need for the US Army soldier missions. These are envisioned to be deployed at the unmanned aerial vehicles; should operate near room temperature, be economic to manufacture, and should minimize the Size, Weight and Power (SWaP) requirements. Quaternary InAsxSbyBi1-x-y alloy was recently proposed as a material system for the fabrication of MWIR and LWIR detectors. It can be grown lattice-matched to the commercially available GaSb substrates while its bandgap energy can be tuned from 0.32 eV to 0.10 eV (4 µm to 12 µm) at low temperatures and from 0.27 eV to 0.042 eV (5 µm to 30 µm) at room temperature. Films of InAsxSbyBi1-x-y need to be grown by Molecular Beam Epitaxy (MBE) at low temperatures to improve Bi incorporation into the crystal lattice. This leads to formation of point defects reducing minority carrier lifetime. The last is extremely important as it determines carrier collection efficiency and serves as a measure of the potential of InAsxSbyBi1-x-y to serve as a detector material Radiation Monitoring Devices (RMD), Inc. will address this problem via a dual approach that will passivate defects states present both in the bulk of InAsxSbyBi1-x-y and at the surface. Bulk alloy defects will be passivated using hydrogenation. Surface defect passivation is achieved via a unique proprietary two-step surface treatment. RMD Inc, will demonstrate ability to process 2-inch wafers in Phase I and will expand towards 4-inch wafers in Phase II.