engleski

Experimental evidence of self-compensation in II-VI compounds

Microscopic origin of full electrical compensation of donor doped CdS, thermally treated under S pressure, was analyzed with Perturbed Angular Correlation (PAC) and Hall effect measurements. Single crystals were implanted with radioactive 111In and stable 115In ions. Total In concentration at peak maximum ranged from 1016 to 1020/cm3. Strong correlation was observed between electrical self-compensation and the formation of (InCd-VCd) pairs (A centers) with thermal annealings. It is shown that the presence of In donors during thermal treatment under S pressure provokes spontaneous formation of (doubly) ionized cation vacancies, [VCd]. During cooling, these vacancies form pairs with In donors (A center), which compensate the rest of donors, leading to highly resistive material. Presented experiments are direct experimental evidence of the basic principle of self-compensation: doped crystals spontaneously creates just a matching concentration of native point defects needed to completely electrically compensate foreign doping atoms. The same mechanism is valid for over 4 orders of magnitude of In concentrations.

self-compensation; CdS; II-VI; doping

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