Simulation of the Influence of Absorber Thickness and Doping Concentration on Non-equilibrium Photovoltaic Long-Wavelength HgCdTe Infrared Detectors

High operating temperature (HOT) detectors, especially state-of-the-art HgCdTe detectors, hold promise for significantly reducing the weight and cost of infrared (IR) detectors. However, HgCdTe detectors suffer from high dark current density dominated by Auger recombination at high working temperatures due to high carrier concentrations. An extremely low doping level is required to decrease the carrier concentration, which is difficult to achieve by molecular beam epitaxy (MBE) due to uncontrollable substrate impurities and equipment background impurities, among other factors. Carriers can also be significantly reduced by creating non-equilibrium working conditions in the HgCdTe detector, where the resulting detector can achieve a low dark current. That dark current is influenced by the thickness and doping level of the absorbers. Herein, we investigated the effects of absorber layer thickness and doping concentration on the dark current of a non-equilibrium photovoltaic long-wavelength (LW) IR HgCdTe detector using Silvaco ATLAS software. It was revealed that the dark current was significantly influenced by the doping level, and a prohibitively low level of doping (5 × 10 13 cm −3 ) was usually required to retain the low dark current. The thickness of the absorber layer could be appropriately designed under a certain doping concentration. Moreover, a higher quantum efficiency via a thinner absorber layer could be achieved by designing an appropriate composition gradient, which effectively increased the signal-to-noise ratio of the detector. This work shows that a high-performance HOT non-equilibrium LW HgCdTe detector can be achieved by optimizing the absorber thickness and Cd composition gradient slope under a relative high doping concentration (1 × 10 14 cm −3 ).