Midwave infrared InSb nBn photodetector

The first demonstration of InSb photodetector with nBn design is reported. The nBn structure, grown by molecular beam epitaxy (MBE) on InSb substrate, is built by using n-type InSb as absorber layer and InAlSb alloy as barrier layer. The nBn detector, showing cut-off wavelength of 5.4 mu m at 77 K in photovoltaic mode, exhibits dark current density as low as 10(-9) A/cm(2) at -50 mV reverse bias, at least two decades lower than usual InSb photodiode.