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 R₀ A of 120 cm², Rmax A of 6000 cm², and a dark current level of 3.5× 10^-5 A cm^-2 at -50 mV bias.