Hg_0.8Cd_0.2Te native defects: Densities and dopant properties

Abstract

We examine the native defect equilibrium in HgCdTe, including cation and anion vacancies, interstitials, and antisites in the analysis. A gradient correction to the local density functional has been added to the defect formation enthalpies calculated within the local density approximation, and preliminary predictions of the dominant ionization states are made. Temperature-dependent defect formation entropies and the temperature dependence of the pre-exponentials are incorporated into the calculation of the defect densities. Degenerate Fermi-Dirac statistics are used for the electronic equilibration, and the intrinsic reaction constant as a function of composition and temperature is calculated. We theoretically substantiate the doubly ionized mercury vacancy as the dominant defect in HgCdTe, and expect the doubly ionized mercury vacancy densities to be comparable in HgZnTe. We predict that tellurium antisites are donors and will be present for some annealing conditions in sufficient quantities to be measured and possibly to affect device performance.