Dark Current Performance Enhancement in Type-II Superlattice Photodetectors via pBn Barrier Engineering

Abstract

Type-II superlattices (T2SLs) are currently technologically favored absorbers for infrared (IR) photodetectors due to their tunable band gap, lower Auger recombination rates, and higher effective masses in comparison to traditional bulk ternary alloys such as HgCdTe. The pBn barrier configuration is usually preferred to improve the dark current characteristics of the InAs/GaSb T2SL IR photodetectors. To investigate conclusively the impact of a barrier on the dark current, we present a comprehensive study featuring a pBn and a p-i-n device configuration at 77 K. In the pBn configuration, the doping levels in the barrier and absorber layer suppress the band-to-band tunneling (BTBT) and the trap-assisted tunneling (TAT) current dominates. In the p-i-n detector, the TAT current prevails with a small contribution of BTBT current near ${V}=-1~\text {V}$ , as a function of absorber doping. It is shown that the pBn detector exhibits 104 times less TAT current when compared with the p-i-n detector at ${V}=-{0.1}~\text {V}$ . As the dark current varies with the number of monolayers of InAs and GaSb in a given period, we then focus on the dark current minimization of three pBn detectors with an absorber layer consisting of a symmetric superlattice (SL), InAs-rich SL, and GaSb-rich SL each with an energy band gap of 0.23 eV. We conclusively ascertain and demonstrate the barrier and absorber configurations along with the bias conditions that minimize the dark currents thereby setting a stage to systematically engineer barriers with the aim of minimizing dark currents via a component-by-component analysis.