PHOTOLUMINESCENCE OF TIN-DOPED GAAS GROWN BY LIQUID-PHASE EPITAXY FROM A MIXED GA-BI SOLVENT

This paper reports the electrical properties and low-temperature photo luminescence of layers of n-GaAs(Sn) grown by liquid-phase epitaxy fro m gallium, bismuth, and mixed gallium-bismuth solvents with different substrate orientations and temperatures. It is shown that the concentr ation of shallow Sn donors increases as the growth temperature is incr eased, and also when the bismuth concentration in the solvent composit ion is increased and when the substrate orientation is changed from (1 00) to (111) B. Lines which are associated with Sn deep acceptors are detected in the photoluminescence spectra. It is shown that the concen tration of compensating accepters increases quadratically with increas ing free-electron concentration and decreases upon lowering the growth temperature and upon introduction of bismuth into the solvent. Layers with the minimum concentration of Sn deep accepters are obtained by e pitaxy from a purely bismuth solvent at a temperature of 700 degrees C . A thermodynamic model of the formation of deep compensating accepter s is constructed. This model makes it possible to explain the observed phenomena. It assumes that a diatomic tin molecule is captured in the growing crystal, after which one of the Sn atoms moves to an intersti tial site. (C) 1996 American Institute of Physics.