Long-Wave InAs/GaSb Superlattice Detectors Based on nBn and Pin Designs

The development of type-II InAs/GaSb superlattice (SL) detectors with nBn and pin designs for the long-wave infrared (LWIR) spectral region is discussed. The dependence of dark current density and responsitivity of the pin photodetectors on doping type and level is investigated, and it is shown that dark current density decreases while responsivity and detectivity increase by p-doping the absorbing region of pin detectors. Comparison of optical and electrical properties of SL photodetectors based on the nBn and pin designs is reported. nBn devices have higher specific detectivity (D*), responsivity, and lower dark current density as compared to the pin detectors. The decrease in dark current in nBn devices is due to suppression of Shockley-Reed-Hall and surface leakage currents. A specific detectivity (D*) of 7.15 × 10⁹ cm Hz^1/2 W^-1 at 0.1 V, a responsivity of 1.28 A/W and a quantum efficiency of 21.3% under 0.2 V biasing at 77 K and 7 ¿m, assuming unity gain, was obtained in the nBn device.