Absorption Characteristics of Mid-Wave Infrared Type-Ⅱ Superlattices

摘要

Mid-wave infrared (MWIR) spectral range has become a spectral region of choice for forward looking infrared sensor systems on military aircraft due to the advantages of greater image contrast, enhanced diffraction-limited resolution, and lower cost focal plane arrays (FPAs) with high operability. Today's MWIR FPA technology is primarily based on mature semiconductor materials such as InSb and HgCdTe; however, the recently emerged MWIR type-Ⅱ superlattice (T2SL) technology is of future interest. Although T2SL material development and device design efforts have advanced to the FPA stage, there are still some areas of basic material research that need to be investigated. One basic area focused in this work is the infrared absorption characteristics of T2SL structures based on both InAs/GaSb and InAs/InAsSb material systems. Optical constants are obtained by infrared transmission spectroscopy and the use of variable angle spectroscopic ellipsometry is also explored. T2SL detectors have proven to be the next candidate for high operating temperature MWIR detectors due to acceptably low dark currents; however, approaching the quantum efficiency of InSb detectors remains a challenge.