EFFECTS OF LOCAL ENVIRONMENT ON LOCALIZED VIBRATIONAL-MODES OF ALUMINUM IN ALXGA1-XAS

Aluminum-related localized vibrational modes in samples of AlxGa1-xAs, which were grown by molecular-beam epitaxy were investigated using Fourier-transform infrared spectroscopy. Three distinct satellite peaks were observed at 358.0, 365.8, and 366.8 cm-1 around the primary peak, due to isolated Al atoms in dilute Alx Ga1-xAs alloys. One of the satellite peaks did not appear in a sample consisting of one monolayer of AlxGa1-xAs sandwiched by GaAs. The satellite peaks are concluded to result from an Al atom perturbed by another Al atom occupying a second-nearest-neighbor site. Three additional small satellite peaks were also observed in alloy samples. We propose a model in which the latter three peaks are caused by an Al atom at a fourth-nearest- neighbor site. © 1990 The American Physical Society.