Nonequilibrium operation of long wavelength HgCdTe photo detectors for higher operating temperatures

Abstract

Our fundamental approach was to increase the operating temperature of the device by reducing the volume of its diffusion region, while maintaining the performance at low temperatures. Reducing the diffusion volume of a detector can be achieved by reducing the active layer thickness, reducing the absorber volume, and reducing the junction area while maintaining the optical area as the original pixel by using micro-lens technology on pixel levels, etc. We are pursuing an infrared device with a unique planar architecture that uses a novel approach in obtaining low arsenic doping concentrations in longwavelength (LW) mercury cadmium telluride (HgCdTe) on CdZnTe substrates for higher temperature applications. We fabricated a p-on-n structure that we term P+/p/N+, where the symbol p indicates a drastically reduced extrinsic p-type carrier concentration (on the order of mid-10 15 cm -3 ); P + and N + denote a higher doping density, as well as a higher energy gap, than the photosensitive base p-region. Fabricated devices indicated that Auger suppression is seen in the P + /p/N + architecture at temperatures above 130 K; we obtained saturation currents on the order of 3 mAmps on 250-μm-diameter devices at 300 K with Auger suppression. Data shows that roughly 50% reduction in dark current is achieved at 300 K due to Auger suppression.