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

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 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 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.

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