Type II Superlattices on Silicon for Infrared Photodetectors

High performance infrared detectors are highly needed for next generation ballistic 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 silicon ROIC that leads to cracking and thus limits the FPA size. It is therefore proposed here to study the feasibility of growing type II InAs/GaSb superlattices on silicon substrates in spite of a lattice mismatch of ~11 %. It is here proposed to demonstrate high quality type II superlattices, single element superlattice photodetectors and pixel arrays on more robust and optically transparent (in the infrared spectral bands of interest) Silicon substrates.