It is a well-known experimental fact that the electrical properties of the A' B"' C;' chalcopyrite semiconductors are largely influenced by growth conditions and annealing procedures from which it has been concluded that intrinsic doping effects play an important role in establishing the electrical characteristics of these compounds (TELL et al. 1972). In the case of CuGaSe, only p-type material has been reported in the literature independent on the preparation technique and annealing conditions (LERNER; MANDEL et al. ; PALATNIK et al. ; TELL et al. 1972; and for CuGaSe, bulk single crystals the predominant formation of Cu vacancies TELL et al. 1972) or Se interstitials (STANKIEWICZ et al.) has been proposed as a possible explanation of this result. In the present communication it is shown that if the partial vapour pressure data of this compound is taken into account this interpretation must be abandoned.
If an A'B"'C1' melt growth experiment is started with a prereacted material having stoichiometric composition then in the resulting as-grown bulk crystals a deviation from this stoichiometry is expected because of the incongruent evaporation of all A'B'I'CZ' compounds (BERGER et al.). According to the vapour pressure studies of STRELCHENKO et al. (1969) Flg 1 . Partial vapour pressure versus temperature for the dissociation products Ga,Se and Se, of CuGaSe, acc. to STRELCHENKO et al. 1969)