Low dark current in mid-infrared type-II superlattice heterojunction photodiodes

A mid-infrared (MWIR, 3-5 μm) InAs/GaSb type-II superlattice (T2SL) photodiode device with very low dark current is presented. The novel heterojunction device is compared to a conventional pn-homojunction device. Photodetectors with reduced dark current allow an increased operating temperature and thus to lower the cooling requirements for high performance infrared imaging applications. We report on a dark current reduction by a factor of more than 100 at a typical operation voltage of −100 mV at 77 K, which was realized merely by device design. This measured dark current is the lowest reported to our knowledge for T2SL-detectors operating in the 3-5 μm range. At the same time, the photo current signal is unaffected by the heterostructure design over the entire bias voltage range.