HgCdTe status review with emphasis on correlations, native defects and diffusion

Abstract

The authors review the current status of knowledge of fundamental properties of the alloy Hg_1-xCd_xTe. The most vexing questions are about its correlation state. Several different experiments now suggest it is highly correlated, but no theory predicts this result. They also discuss other properties, including dislocations at interfaces, the residual donor, worms, surface segregation and its impact on passivation, and concentration fluctuations. The forces driving these phenomena, where they are known, will be presented. Most of the paper focuses on the following: correlations; native defects, formation enthalpies and entropies; native defect equilibria with mercury gas and with tellurium inclusions; and self-diffusion coefficient activation energies including its contribution from migration energies. They will take advantage of new first-principles, high-accuracy calculations to help explain the experimental situation. The calculations predict that the main native defects found in alloys equilibrated at low Hg pressures are Hg vacancies, while at high Hg pressures they are Hg interstitials, and, surprisingly, Hg antisites.