Studies were made of 0.96 and 0.84eV photoluminescence emissions, at various temperatures, in GaAs epilayers that had been grown onto Si, with [As]/[Ga] = 20 to 50, by means of metalorganic chemical vapor deposition. The thermal activation energy and Franck-Condon shift for the 0.96eV emission band were obtained by measuring variations in its photoluminescence intensity and full-width at half-maximum, respectively. It was found that the temperature dependence of the intensity of the 0.84eV photoluminescence emission could not be fitted by an Arrhenius relationship. On the other hand, it could be fitted with an expression that was normally used for amorphous semiconductors or localized states. This permitted the emission to be correlated with the presence of defects in hetero-epitaxial GaAs layers on Si. By taking account of the Franck-Condon and band-gap shifts, the 0.96eV emission could be attributed to the recombination luminescence of donor-acceptor pairs that comprised an As vacancy and a Ga vacancy. The 0.84eV emission was attributed to a transition, from a localized As interstitial plus Ga vacancy complex center, to a Ga vacancy.

J.Liang, J.Jiang, J.Zhao, Y.Gao: Journal of Applied Physics, 1996, 79[9], 7173-6