Toward realization of small-size dual-band long-wavelength infrared photodetectors based on InAs/GaSb/AlSb type-II superlattices

In this study, we demonstrate 12 × 12 µm2 high-performance, dual-band, long-wavelength infrared (LWIR) photodetectors based on InAs/GaSb/AlSb type-II superlattices. The structure consists of two back-to-back heterojunction photodiodes with 2 µm-thick p-doped absorption regions. High quality dry etching combined with SiO2 passivation results in a surface resistivity value of 7.9 × 105 Ω cm for the longer (red) channel and little degradation of the electrical performance. The device reaches dark current density values of 4.5 × 10−4 A/cm2 for the longer (red) and 1.3 × 10−4 A/cm2 for the shorter (blue) LWIR channels at quantum efficiency saturation. It has 50% cut-off wavelengths of 8.3 and 11.2 µm for the blue and red channel, respectively, at 77 K in back-side illumination configuration and exhibits quantum efficiencies of 37% and 29%, respectively. This results in specific detectivity values of 2.5 × 1011 cm·Hz1/2/W and 1.3 × 1011 cm·Hz1/2/W at 77 K.