Design of Band Engineered HgCdTe nBn Detectors for MWIR and LWIR Applications

In this paper, we present a theoretical study of mercury cadmium telluride (HgCdTe)-based unipolar n-type/barrier/n-type (nBn) infrared (IR) detector structures for midwave IR and longwave IR spectral bands. To achieve the ultimate performance of nBn detectors, a bandgap engineering method is proposed to remove the undesirable valence band discontinuity that is currently limiting the performance of conventional HgCdTe nBn detectors. Our proposed band engineering method relies on simultaneous grading of the barrier composition and doping density profiles, leading to efficient elimination of the valence band discontinuity. This allows the detector to operate at |V
_bias
| <;50 mV, rendering all tunneling-related dark current components insignificant and allowing the detector to achieve the maximum possible diffusion current limited performance.