Effects of Ga concentration on electronic and optical properties of Ga-doped ZnO from first principles calculations

This study evaluated the electronic and optical properties of Ga-doped ZnO with various concentrations of gallium, employing first principles calculations based on density functional theory and the Hubbard U (DFT + U-d + U-p). The lattice constants and band gap of ZnO calculated in this study are in agreement with experimental values. Results show that donor concentration increases with an increase in Ga concentration; however, electrical conductivity is reduced when localized states close to the Fermi level and higher scattering probability of free electrons occur with high Ga concentration. Following the incorporation of Ga into ZnO (1.4-6.3 at.%), the average transmittance of light in both the visible and UV ranges exceeds that of ZnO. However, the stronger and wider donor states obtained from high doping levels (12.5-25 at.%) significantly decreases the average transmittance. Thus, selecting a suitable doping level is crucial to optimizing the photoelectric performance of Ga-doped ZnO. This study also provides a theoretical explanation for the factors influencing these properties. (c) 2012 Elsevier B.V. All rights reserved.