Feasibility Study of the Growth of Type II InAs/GaSb Superlattice on GaAs for Infrared Applications

High performance infrared detectors in the mid and long wavelength infrared (MWIR and LWIR) spectral bands are highly needed in a number of missile defense missions. Type II InAs/GaSb superlattices represent the most promising material system capable of delivering a more affordable and producible focal plane array (FPA) technology than the current technology, while at the same time exhibiting similar or better performance. Two of the major challenges in the realization of FPA in this system pertain to the unintentionally doped p-type GaSb substrate used in the growth of type II superlattices: its strong infrared absorption and its thermal mismatch with the ROIC that leads to cracking upon hybridization and thus limits the FPA size. It is here proposed to study the feasibility of growing type II InAs/GaSb superlattices on GaAs substrates in spite of a lattice mismatch of ~7 %. The use GaAs is expected to avoid the substrate absorption issue since GaAs is transparent in the infrared spectral bands of interest, and alleviate the cracking issue since GaAs is harder than GaSb. The design and optimization of an appropriate buffer layer technique that leads to high quality GaSb will be an essential part of the proposed work.