GaSb for passivating type-II InAs/GaSb superlattice mesas

The lack of stable passivation for mesa sidewalls is hampering the development of infrared focal plane arrays (FPAs) based on type-II InAs/GaSb superlattices (SL). We propose the use of GaSb itself to fill the space between FPA pixels, thus eliminating sidewalls and sidewall currents. In such a structure, the conduction band discontinuity between the SL and the GaSb encapsulant constrains electrons to move vertically between the contacts, while the low, vertical hole mobility causes holes to preferentially move transversely. Hence, this scheme (a) eliminates surface leakage currents, which improves detectivity and (b) reduces the density of excess holes in the active region of the device, which improves Shockley–Reed–Hall and direct recombination lifetimes, thereby the detector operating temperature and figures of merit.