Revealing the influence of annealing on mid- and long-wave infrared dual-color HgCdTe p–n junctions at the nanometer scale

Abstract

Doping and activation in HgCdTe to form p–n junctions are prerequisites for achieving superior infrared detection performance. This process is complex and highly sensitive to heat treatment. Comprehensive understanding of this procedure is often impeded by the lack of electronic information in the material with high spatial resolution. In this study, the carrier distributions of mid- and long-wave infrared (MWIR-LWIR) dual-color HgCdTe after annealing at different temperatures were investigated through scanning capacitance microscopy (SCM). The p-type region width of the 410 °C-annealed sample was 0.13 μm wider than that of the sample annealed at 380 °C. Accordingly, the arsenic impurity concentrations at which the p-to-n-type transition occurred were determined to be 1.85 × 10¹⁷ cm⁻³ and 2.33 × 10¹⁷ cm⁻³ for the two samples, respectively. The widths of the p–n junction were determined at temperatures ranging from 233 K to 293 K. The decrease in junction width on the MWIR side of the 410 °C-annealed sample mainly originated from the increase in the intrinsic carrier concentration with temperature. In contrast, the junctions in the sample annealed at 380 °C showed considerably greater shrinkage, which signifies the influence of dopants while approaching room temperature. The discovery of microscopic electrical properties in this study has been partially verified through Hall measurements, contributing to the evaluation of the doping process and optimizing the performance of p–n junctions.