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 $10.5μm$ cutoff wavelength exhibit an $R0A$ of $120Ωcm2$⁠, $RmaxA$ of $6000Ωcm2$⁠, and a dark current level of $3.5×10−5Acm−2$ at −50 mV bias.