Material Perspective on HgTe Nanocrystal-Based Short-Wave Infrared Focal Plane Arrays

Abstract

After the use of nanocrystals as light downconverters, infrared sensing appears to be one of the first market applications where they can be used while being both electrically and optically active. Over recent years, tremendous progress has been achieved, leading to an apparent rise in the technological-readiness level (TRL). So far, the efforts have been focused on PbS nanocrystals for operation in the near-infrared. Here, we focus on HgTe since its narrower band gap offers more flexibility to explore the extended short-wave and midwave infrared. We report a photoconductive strategy for the design of short-wave infrared focal plane arrays with enhanced image quality. An important aspect often swept under the rug at an early stage is the material stability. It appears that HgTe remains mostly unaffected by oxidation under air operation. The evaporation of Hg, a potentially dramatic aging process, only occurs at temperatures far beyond the focal plane array’s standard working temperature. The main bottleneck appears to be the particle sintering resulting from joule heating of focal plane arrays. This suggests that a cooling system is required, whose first role is to prevent the material from sintering even before targeting dark current reduction.