Reactions conjectured to occur during the cooldown of GaAs grown from
the melt are presented. These are used to fit existing data on the dep
endence of various concentrations (carrier, EL2, and ELS) on melt comp
osition in crystals grown from a Ga-rich melt doped with silicon. Acce
ptable fits are based on the following model assumptions: (1) EL2 is A
sGaVGa, (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 conce
ntration in the crystal. (C) 1995 American Institute of Physics.