Surface leakage current reduction in long wavelength infrared type-II InAs/GaSb superlattice photodiodes

Dielectric passivation of long wavelength infrared type-II InAs/GaSb superlattice photodetectors with different active region doping profiles has been studied. SiO2 passivation was shown to be efficient as long as it was not put in direct contact with the highly doped superlattice. A hybrid graded doping profile combined with the shallow etch technique reduced the surface leakage current in SiO2 passivated devices by up to two orders of magnitude compared to the usual design. As a result, at 77 K the SiO2 passivated devices with 10.5 μm cutoff wavelength exhibit an R0A of 120 Ω cm2, RmaxA of 6000 Ω cm2, and a dark current level of 3.5×10−5 A cm−2 at −50 mV bias.