Effect of Heat Treatment on the 1.370 eV Photoluminescence Emission Band in Zn-Doped GaAs

A number of changes in the 1.370 eV photoluminescence band are observed in Zn-doped GaAs after heat treatment in molten KCN, Ga, or diffusion with Cu at temperatures ranging from 235° to 1100°C. The band is replaced by a CuGa− band at 1.356 eV after Cu diffusion under intrinsic conditions and can be eliminated or preserved, respectively, by heat treating the crystal in molten KCN or Ga above 650°C. Emission of a broad band near 1.37 eV with a sharp-line structure appears after saturation with Cu at temperatures between 550° and 370°C. The structure has a zero-phonon line at 1.429 eV and additional lines separated by about 0.011 eV. No change in the shape of the 1.370 eV band is seen for heat treatment below 550°C in the absence of copper. It is proposed that the centers associated with the 1.370 eV band are VAsZnGa or DAsZnGa pairs, where VAs and DAs denote an As vacancy and a donor impurity occupying an As site, and that the centers responsible for the band with sharp-line structure are VAsCuGa or DAsCuGa pairs. The sharp-line structure probably involves emission of local-mode phonons resulting from the pair substituting for a Ga–As pair in the crystal.