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

• Published in: Optical materials 2013-01, Vol.35 (3), p.509-515
• Main Authors: Wu, Hsuan-Chung, Peng, Yen-Chun, Chen, Chieh-Cheng
• Format: Article
• Language: English
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; DFT + U; Doping; Electron states; Electronic structure; Electronics; Exact sciences and technology; Fermi level; Fermi surfaces; First principles; Fundamental areas of phenomenology (including applications); Ga-doped ZnO; Gallium; Mathematical analysis; Methods of electronic structure calculations; Optical constants: refractive index, complex dielectric constant, absorption, reflection and transmission coefficients, emissivity; Optical materials; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of bulk materials and thin films; Optical property; Optics; Other nonlinear optical materials; photorefractive and semiconductor materials; Physics; Transmittance; Zinc oxide
• ISSN: 0925-3467; 1873-1252
• DOI: 10.1016/j.optmat.2012.10.022

► Photoelectric properties of Ga-doped ZnO have been investigated using DFT+Ud+Up. ► Calculated and experimental values of band gap were consistent. ► At low Ga at.%, average transmittance is higher than that of ZnO. ► At high Ga at.%, donor states decrease transmittance and conductivity. 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+Ud+Up). 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 (1.4–6.3at.%), 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 (12.5–25at.%) 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.