Theoretical investigation of the electrical and optical activity of vanadium in GaAs

We study the excitation and ionization processes at the isolated substitutional vanadium impurity in GaAs. The electronic structure is solved through the spin-restricted version of the multiple-scattering Xα method to obtain the relevant mean-field energies, and correlation effects are evaluated through the Fazzio-Caldas-Zunger multiplet approach. The similar systems GaP:V, InP:V are also investigated. Our results for GaAs:V point to the occurrence of an acceptor level at ∼$E_c$-0.16 eV, the donor level appearing very close to or within the valence band. The V-related midgap acceptor should then be related to some complex defect involving vanadium. We also suggest that ${\mathrm{V}}^{2+}$ in these compounds is present in the low-spin ground state ${}_{}{}^2{}_{}{}^{}\mathrm{E}$..AE