Defect structure of CdSe in selenium vapour

High temperature measurements of charge carrier densities and mobilities versus pressure of selenium vapour are performed both in p-type undoped CdSe samples and n-CdSe doped by either donors (In) or acceptors (Cu). For undoped p-CdSe crystals in the temperature range from 850 to 1000 K the neutrality equation may be approximated as p = 2VCd−-, if the selenium pressure does not differ from the saturation pressure by one and half order of magnitude. A theoretical calculation of isothermal dependences of charge carriers on the pressure of selenium vapour is in a good agreement with experimental data. It is found that hole conductivity of CdSe crystals at room temperature is due to the cadmium vacancies with ionization energy E = Ev + (0.30 to 0.36) eV. Experimental and theoretical data for doped CdSe crystals have shown that the density of In or Cu impurities at the cadmium sites is temperature dependent and these impurities are neutral at the interstitial sites.