It was recalled that the solubility of native point defects and dopants in semiconductors depended upon the growth temperature, crystal stoichiometry and Fermi-level position. At high temperatures, III¯V compounds contained high concentrations of mainly charged native point defects. Published titration and density/lattice-parameter measurements of GaAs had shown conclusively that melt-grown crystals contained about 1019/cm3 of As vacancies and As interstitials at the melting point. The As vacancies formed a relatively shallow (Ec - 0.1eV) donor state. The concentrations of these ionized vacancies at the melting point of GaAs, and under the conditions used for liquid-phase epitaxial growth from Ga-solution, exceeded the intrinsic electron¯hole concentration. These ionized vacancies therefore controlled the electro-neutrality of the crystal and the position of the Fermi level during growth under these conditions. The As-vacancy concentration deduced from titration measurements, when inserted into a comprehensive equilibrium thermodynamic description of the system, accurately predicted the observed ranges of linear dopant solubility found for group-IV and group-VI donor dopants. The current hypothesis, that this linear range was governed by a non-equilibrium incorporation process governed by a Schottky barrier at the crystal/melt interface, was here deemed to be unnecessary. It was shown that donor and acceptor dopant incorporation, EL2 formation and the annealing behaviour could all be fully explained by the thermodynamic model. The differing doping behaviour exhibited by other zincblende III¯V compounds was shown to be related to the differing relative numbers of native point defects on the 2 sub-lattices.

Charged Native Point Defects in GaAs and Other III-V Compounds. D.T.J.Hurle: Journal of Crystal Growth, 2002, 237-239, 1621-7