Design and demonstration of InAs/GaInSb strained-layer superlattices optimized for long-wavelength infrared detectors

The {dollar}rm InAs/Gasb{lcub}1-x{rcub}Insb{lcub}x{rcub}Sb{dollar} strained-layer superlattice (SLS) holds promise as an alternative III-V semiconductor material for long wavelength {dollar}({lcub}>{rcub} 10 mu m){dollar} infrared detectors. The energy gap and optical properties of this superlattice can be widely adjusted by varying its structural parameters. Along with this flexibility comes the complexity of optimizing the SLS structures for a particular infrared detector application. Band structure modeling and material characterization of experimental samples are used to develop an explicit optimization scheme for maximizing the absorption at a given energy gap. Optimal SLS structures are then bandgap engineered for incorporation into double-heterojunction photovoltaic devices. These device structures were designed to maximize the quantum efficiency while minimizing transport barriers at the heterointerfaces. At 78 K, these devices exhibit rectifying behavior and long-wavelength photovoltaic response out to a wavelength of 10 {dollar}mu m,{dollar} corresponding to the narrow SLS energy gap. The photodiodes are assessed through the correlation of their performance with the material properties of the superlattice and the detector design. The analysis reveals that while the detectors' electrical properties are immature, high quantum efficiency is achieved. To the author's knowledge, these devices demonstrate the highest detectivity performance yet reported for any III-V long-wavelength detector of comparable absorbing thickness.