Viability of HgCdTe-Based Two-Color nBn Infrared Detectors

Abstract In this study, we have undertaken the design and simulation of an nBn, sequential-readout, two-color detector with two absorbers and a barrier: a very-long-wavelength infrared (VLWIR) type III superlattice (T3SL) HgTe/CdTe with a cutoff of 14 µm, a long-wavelength infrared bulk alloy HgCdTe with a cutoff of 9 µm, and an extended short-wavelength infrared barrier T3SL HgTe/CdTe with a cutoff of 4.35 µm. We employed a 14-band k·p method band structure calculation of the alloy and superlattice. The VLWIR superlattice absorber exhibits a distinct absorption onset. The band structures of both absorbers align well with the literature. By engineering the superlattices’ band structures and adjusting the doping levels, we successfully achieved a zero-valence band offset (VBO) in an nBn device architecture with T3SLs as the barrier and the absorber layer. Additionally, our proposed structure is predicted to produce reduced dark currents compared to the theoretical model developed by our co-author, Peihong Man, in his thesis. Man’s foundational work proposed a novel nBn architecture employing a HgTe/CdTe superlattice barrier engineered to minimize VBOs, which serves as the benchmark for this study, indicating promising performance. Our device offers a viable solution to overcome the challenges associated with high-temperature annealing and p -type doping due to the absence of p -type layers, thereby mitigating the issue of superlattice layer intermixing in photodetector applications.