THEORY OF EL2 AND EL5 FORMATION IN MELT-GROWN GAAS-SI

Reactions conjectured to occur during the cooldown of GaAs grown from the melt are presented. These are used to fit existing data on the dependence of various concentrations (carrier, EL2, and ELS) on melt composition in crystals grown from a Ga-rich melt doped with silicon. Acceptable fits are based on the following model assumptions: (1) EL2 is AsGaVGa, (2) EL5 is the acceptor complex SiGaVGa, and (3) freeze-out of the reaction V-Ga+AsGaVAs = AsGaVAsVGa during cooldown is responsible for a large V-Ga concentration and a concomitant restricted EL2 concentration in the crystal. (C) 1995 American Institute of Physics.