The infrared vibrational absorption spectrum of the Si-X defect present in heavily Si doped GaAs

Heavily silicon doped GaAs grown by molecular beam epitaxy using a single gallium isotope source (Ga-69) has been studied by infrared absorption to reveal localized vibrational modes (LVMs) of Si complexes. The structure observed close to 367 cm(-1) is the same as that present in normal GaAs:Si spectra and does not result from mixed Ga isotopes. The electron trap Si-X gives three LVMs at 368.4, 370.0, and 399.6 cm(-1), typical of second neighbor donor-acceptor pairs, but inconsistent with a previous proposal that its structure is the planar defect V-Ga-Si-As-As-Ga. It is now suggested that the defect is a perturbed Si-Ga-V-Ga center, involving a second Si atom or a second vacancy. (C) 1997 American Institute of Physics.