Study on optical properties of the F type color center in the p-CuAlO2 crystal with first principles

Abstract

CuAlO2 is an important candidate for p-type transparent conducting oxides (TCO). However, the presence of oxygen vacancy will seriously reduce the transparency of the crystal and oxygen vacancy as donor defect will restrain p-type doping. In this paper, the defect formation energy of an oxygen vacancy in different charge states has been studied by density functional theory. The band edge is adjusted by hybrid density functional method. The finite-size correction scheme (FNV method) is used to correct the supercell defect formation energy of the charged defects. The defect transition level is not close to the bottom of the conduction band, which indicates that the oxygen vacancy has no obvious effect on conductivity. Therefore, the optical spectrum of the F/F+ center containing the electron-phonon coupling has been obtained. The absorption peaks of the F and F+ centers are located at 2.29 eV and 1.47 eV, respectively. The emission peaks of the F and F+ centers are located at 2.06 eV and 1.30 eV, respectively. These results indicate that the presence of oxygen vacancy reduces the transparency of the crystal in the visible range. It is speculated that the emission band of the 558 nm (2.22 eV) originates from the F center. The absorbed band of the 1.65 eV–2.10 eV is attributed to oxygen vacancy. It is necessary to suppress the formation of oxygen vacancies.