Ab-initio study of the structural, electronic and optical properties of ZnO co-doped gallium aluminum Zn1−x−yGaxAlyO

Structural, electronic and optical properties of pure ZnO and Ga, Al co-doped ZnO with different concentrations Zn1−xGaxAlyO up to (x, y) = (25, 12.5) % in the wurtzite phase are studied using the ab-initio full-potential linearized augmented plane wave (FP-LAPW) method, with the exchange and correlation potential within the generalized gradient approximation (GGA) and the modified Becke-Johnson (mBJ) exchange potential. The band gap and lattice parameters calculated for pure ZnO are in a good agreement with other theoretical calculations and experimental results. The absorption spectra of pure ZnO increases in the visible range, whereas the reflectivity decreases down to the UV range. The doping of ZnO with Ga and Al ions creates shallow donor Ga-4s and Al-3s states around the Fermi level in the minimum of the conduction band yielding to the increase of the optical band gap, the conductivity and the reflectivity, but induces an opposite effect on the absorption.