DOPING OF EPITAXIAL GAAS FILMS BY A ZN ACCEPTOR IMPURITY DURING LIQUID-PHASE EPITAXY FROM GA-BI MOLTEN SOLUTIONS

The processes occurring during doping of GaAs films with the Zn accept or impurity in the course of liquid phase epitaxy from a molten Ga-Bi solution has been studied. The dependence of the thickness of the epit axial GaAs:Zn:Bi films on the composition of the molten solution was f ound to be complex. This complexity is attributed to the complex shape of the liquidus curves of the Ga-Bi-As system and changes in the mass transfer processes occurring in the microinhomogeneous liquid phase. A study of the photoluminescence combined with layer-by-layer etching and the van der Pauw method was used to determine the behavior of the Zn impurity atoms in epitaxial films, on substrates, and on control su bstrates used during growth. The nonlinear dependence of the Zn concen tration in GaAs films on the Bi content in the Ga-Bi solvent was expla ined by a change in the vacancy concentration in the gallium sublattic e and by the nature of the diffusion of Zn in the liquid phase. A cons tant dopant concentration in an epitaxial GaAs film obtained at a give n composition of the solvent indicates that the main doping mechanism is the capture of the Zn impurity atoms from the liquid phase during g rowth.