Native point defect equilibria and the phase extent of gallium arsenide

It is shown that recently revised data on the equilibrium arsenic pressure over Ga:As melts resolves the discrepancy between published determinations of non-stoichiometry in GaAs, obtained from titration and density/lattice parameter measurements. By analysing data on donor solubility in crystals grown from Ga-Bi solutions, an experimental measure of the concentration of charged gallium vacancies is obtained for the first time. This model of equilibrium dopant incorporation is shown to provide a much more satisfactory description than the commonly accepted concept of incorporation controlled by a Schottky barrier at the growth interface. The deduced values of the concentrations of the dominant point defects are used to construct the GaAs solidus.