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The electrical conductivity σ of undoped and Cu‐doped CdSe crystals is measured over the range 600 to 1000°C as a function of cadmium and selenium vapour pressure and temperature. The formation enthalpy of the doubly ionized native donor defect (V Se‥ or Cd i‥) is found to be (1.86 ± 0.09) eV at constant cadmium vapour pressure and ⪆ 4.95 eV at constant selenium vapour pressure. For Cu‐doped samples the conductivity varies as pCd1/2 and the electron concentration is almost independent of temperature above 600°C in Cd vapour. The results are interpreted in terms of a distribution of Cu on the substitutional and interstitial sites. The association between Cu and the native defects is taken into account.

High‐temperature conductivity and copper solubility in CdSe is measured over the range 600 to 900°C as a function of temperature and cadmium and selenium vapour pressure. It is found that in cadmium vapour (pCd > 10−1 atm) below 750°C the main part of copper is in electrically inactive form and with increasing temperature transfers to the electrically active interstitial form Cu i˙ The activation energy of transference is found to be (2.0 ± 0.28) eV. In cadmium vapour the incorporation of copper occurs by the mechanism of controlled electronic imperfections with the electroneutrality condition (ENC) n = Cui and in selenium vapour by the mechanism of controlled atomic imperfections with ENC Cu i˙ = (Cu i˙VCd)′.

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