High performance type-II InAs/GaSb superlattice infrared photodetectors with a short cut-off wavelength

This work investigates the potential of InAs/GaSb superlattice detectors for the short -wavelength infrared spectral band. A barrier detector structure was grown by molecular beam epitaxy and devices were fabricated using standard photolithography techniques. Optical and electrical characterisations were carried out and the current limitations were identified. The authors found that the short diffusion length of similar to 1.8 mu m is currently limiting the quantum efficiency (double-pass, no anti-reflection coating) to 43% at 2.8 mu m and 200 K. The dark current density is limited by the surface leakage current which shows generation-recombination and diffusion characters below and above 195 K, respectively. By fitting the size dependence of the dark current, the bulk values have been estimated to be 6.57 center dot 10(-6)A/cm(2) at 200 K and 2.31 center dot 10(-6) A/cm(2) at 250 K, which is only a factor of 4 and 2, respectively, above the Rule07.