InAs/GaSb strained layer superlattice detectors with nBn design

We have investigated the electrical and optical properties of an nBn based Type-II InAs/GaSb strained layer superlattice detector as a function of absorber region background carrier concentration. Temperature-dependent dark current, responsivity and detectivity were measured. At T = 77 K and V_b = 0.1 V, with two orders of magnitude change in doping concentration, the dark current density increased from ～0.3 mA/cm² to ～0.3 A/cm². We attribute this to a depletion region that exists at the AlGaSb barrier and the SLS absorber interface. The device with non-intentionally doped absorption region demonstrated the lowest dark current density (0.3 mA/cm² at 0.1 V) with a specific detectivity D¹ at zero bias equal to 1.2 × 10¹¹ Jones at 77 K. The D¹ value decreased to 6 × 10¹⁰ cm Hz^1/2/W at 150 K. This temperature dependence is significantly different from conventional PIN diodes, in which the D¹ decreases by over two orders of magnitude from 77 K to 150 K, making nBn devices a promising alternative for higher operating temperatures.