Gallium-isotope fine structure of impurity modes due to defect complexes in GaAs

Abstract

A comprehensive Green’s-function calculation was performed in order to understand the recent high-resolution Fourier-transform infrared absorption (FTIR) data of localized vibrational modes (LVM’s) due to isolated (${\mathrm{Si}}_{\mathrm{Ga}}$ donor, ${\mathrm{B}}_{\mathrm{Ga}}$ isoelectronic, ${\mathrm{Si}}_{\mathrm{As}}$, ${\mathrm{Li}}_{\mathrm{As}}$, ${\mathrm{B}}_{\mathrm{As}}$ acceptor) and pair (${\mathrm{Si}}_{\mathrm{Ga}}$-${\mathrm{Si}}_{\mathrm{As}}$, ${\mathrm{Si}}_{\mathrm{Ga}}$-As-${\mathrm{Li}}_{\mathrm{Ga}}$) defects in GaAs. For the defect centers with $T_d$, $C_{3v}$, $C_s$, and $C_{2v}$ symmetries, we have considered simple perturbation models using mass changes at the impurity sites and nearest-neighbor (NN) force-constant changes between impurity-host atoms.