Design Parameters for High-Performance HgCdTe-Based nBn Detectors Structures

We present a theoretical study of a novel design strategy which significantly improves the performance of mercury cadmium telluride (HgCdTe) unipolar n-type/Barrier/n-type (nBn) infrared detectors for the midwave and longwave infrared applications. The strategy consists of removing the valence band offset between the barrier and the n-type absorber layer, which is the key issue that currently limits the performance of HgCdTe-based nBn detectors. Eliminating the valence band offset allows the detector to operate at │VBias│< 50 mV, thus rendering insignificant all tunnelling-related dark current components and allowing the detector to achieve the maximum possible performance. Furthermore, it is shown that an nBn device architecture allows much higher doping levels to be used in the n-type absorber layer, thus reducing diffusive-related dark currents and projecting enhanced performance at higher operating temperatures. This is in contrast to photovoltaic detectors where the maximum absorber layer doping is limited due to the onset of tunnelling-related dark currents.