Compensating defects and electrical activation of donors in CdS

Abstract

Electrical deactivation of donors in CdS was studied by using Perturbed γγ Angular correlation (PAC) spectroscopy and temperature dependence of Hall mobility, resistivity, and free-carrier concentration. PAC spectra and electrical properties were monitored as a function of thermal treatment either under S or Cd pressure in a temperature range from RT to 1073 K. For samples annealed above 800 K under S pressure, Hall effect showed increased electrical compensation whereas PAC detected spontaneous creation of cadmium vacancies, VCd, via the formation of (InCd–VCd) pairs. The increase of the concentration of compensating acceptors, determined from electrical measurements, precisely correlates with the increase of the concentration of (InCd–VCd) pairs found by means of PAC. In contrast to that, thermal treatment under Cd pressure up to 1073 K does not provoke the formation of compensating native defects up to [In] >1019/cm3.