Strained Layer Superlattice Using HgTe for VLWIR Detection

High-performance detectors sensing in the long wavelength and very long wavelength infrared spectral ranges are desirable for various applications supporting Air Force and Missile Defense capabilities. Limited types of detectors and arrays are currently available for the detection of infrared radiation with wavelengths longer than 15 microns, and most are based on low quantum efficiency extrinsic semiconductors. Despite considerable progress in bulk HgCdTe photovoltaic technology, difficulties persist in sensing wavelengths longer than 10 microns with a bulk material due to limitations imposed by large tunneling dark currents and Auger recombination rates. Strained layer superlattices using HgTe layers and lattice mismatched layers based on CdTe alloys are an extremely promising alternative for infrared systems requiring higher temperature and longer wavelength operation. In this type of superlattice, the active region layers are strained, playing a crucial role in suppressing Auger recombination and therefore increasing the operating temperature of the infrared sensing devices above current standards. The presence of a novel type of detector material based on II-VI strained layer superlattice will not only pave the way to emerging research but will also have an impact on a U.S. market that requires high quality detectors sensitive to very long wavelength infrared radiation.