Comparison of superlattice based dual color nBn and pBp infrared detectors

Long-wave infrared (LWIR) detector technologies with the ability to operate at or near room temperature are very important for many civil and military applications including chemical identification, surveillance, defense and medical diagnostics. Eliminating the need for cryogenics in a detector system can reduce cost, weight and power consumption; simplify the detection system design and allow for widespread usage. In recent years, infrared (IR) detectors based on uni-polar barrier designs have gained interest for their ability to lower dark current and increase a detector's operating temperature. Our group is currently investigating nBn and pBp detectors with InAs/GaSb strain layer superlattice (SLS) absorbers (n) and contacts (n), and AlGaSb and InAs/AlSb superlattice electron and hole barriers (B) respectively. For the case of the nBn structure, the wide-band-gap barrier material (AlGaSb) exhibits a large conduction band offset and a small valence band offset with the narrow-band-gap absorber material. For the pBp structure (InAs/AlSb superlattice barrier), the converse is true with a large valence band offset between the barrier and absorber and a small or zero conduction band offset. Like the built-in barrier in a p-n junction, the heterojunction barrier blocks the majority carriers allowing free movement of photogenerated minority carriers. However, the barrier in an nBn or pBp detector, in contrast with a p-n junction depletion layer, does not contribute to generation-recombination (G-R) current. In this report we aim to investigate and contrast the performance characteristics of an SLS nBn detector with that of and SLS pBp detector.