Self-compensation in CdTe〈Cl〉 in the presence of phase equilibrium of the system crystal-cadmium (tellurium) vapor

Abstract

The self-compensation of charged point defects in CdTe〈Cl〉 is investigated down to the lower limit of free-carrier densities (n _i ,p _i ) over the entire range of vapor pressures P _Cd and P _Te in equilibrium of the crystal-gas phases during annealing. Under conditions where P _Te2 is controlled during annealing of the crystal, the electron density n is observed to increase from 10⁷ cm⁻³ to 10¹⁴ cm⁻³ as P _Te increases from P _min to CdTe〈Te〉 saturation. This result is attributed to the formation of a Te_Cd antistructural defect. The appearance of Te_Cd in the crystal lowers the concentration of cadmium vacancies to the point that the mechanism of exact self-compensation of CdTe〈Cl〉 is disrupted, and low-resistivity n-type crystals are obtained. The data obtained on the concentration p(n) as a function of P _Te2 is used to plot the total n-n _i -p _i dependence with the variation of P _Cd-P _Te2, reflecting the state of point defects in CdTe〈Te〉. The procedure for annealing crystals in two-phase crystal-gas equilibrium is used to reversibly induce n _i -p _i inversion of the electrical conductivity of the crystal.