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 (ni,pi) over the entire range of vapor pressures PCd and PTe in equilibrium of the crystal-gas phases during annealing. Under conditions where PTe2 is controlled during annealing of the crystal, the electron density n is observed to increase from 107 cm−3 to 1014 cm−3 as PTe increases from Pmin to CdTe〈Te〉 saturation. This result is attributed to the formation of a TeCd antistructural defect. The appearance of TeCd 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 PTe2 is used to plot the total n-ni-pi dependence with the variation of PCd-PTe2, 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 ni-pi inversion of the electrical conductivity of the crystal.