First-principles study on electronic and optical properties of transparent conducting oxide CuBO2

Abstract

In this work we study the electronic and optical properties of the new p-type transparent conducting oxide CuBO2. Firstly, after optimizing its lattice parameters, a band structure is calculated by density functional theory with local density approximation (DFT-LDA), on-site Coulomb interaction (LDA+U), quasi-particle approximation (GWA) and Tran and Blaha’s modified Becke–Johnson exchange–correlation potentials (TB09). Both LDA+U and G0W0 calculations are accurate for the indirect band gap, but fail for the direct one. While QPscGW calculations do perturbative corrections to both G0W0 indirect and direct band gap in the same amount, it is leading to an overestimation of the indirect band gap and an underestimation of the direct one at the same time. Besides, the indirect and direct band gap of the optimized lattice parameters are calculated by ABINIT code with TB09 exchange functional and they are underestimated by about 1% and 17%, respectively. For comparison purposes with the experimental values, the band structure is also calculated by ELK code with TB09 and with a minuscule amount of charge removed from its primitive unit cell. With a charge removal by 0.86 both band gaps are very close to the experimental values, with an error of about 0.2% for the indirect band gap and about 0.9% for the direct one. Finally, the dielectric function and optical conductivity of the bulk CuBO2 are calculated by random phase approximation (RPA) and time-dependent density functional theory (TDDFT) on top of the TB09 electronic structure.