Type-II Superlattice Heterostructures for Infrared Detection

Antimonide (Sb) material based Type-II strained layer superlattice (SLS) heterostructures are investigated for long-wave infrared (LWIR) detection. At typical operating temperatures (T~77 K), the dark current of Type-II SLS homojunction LWIR detectors is dominated by the Shockley-Read-Hall (SRH) generation-recombination (g-r) process in the space-charge (depletion) region besides surface leakage. In order to suppress this dark current, a wide bandgap region next to the absorber layer, i.e., heterojunction, has been included in SLS designs. A series of heterojunction-based LWIR SLS detectors with various doping and barrier profiles have been designed and characterized. The significance of the doping profile and thickness of the wide-bandgap layer in optimization of the heterojunction-based SLS detector performance are exhibited from the modeling and experimental results of these devices.