Hybrid density functional theory study of substitutional Gd in ?-Ga2O3

Substitutional Gd alloying in beta-Ga2O3 is studied using hybrid density functional theory. Calculations of structural properties reveal a monotonic increase in lattice parameters, volume and interplanar spacing with increasing Gd content. Cohesive energy and formation energy calculations show monotonically decreasing energy for increased Gd concentrations, implying stability even for large concentration Gd alloying. Partial density of states and electronic band structures reveal that Gd substitution does not result in any inter band gap states, a requirement for p-type conductivity. The electronic band gap does, however, decrease with increasing Gd content where the pronounced Gd levels are deep lying f-orbital electronic states. The frequency dependent dielectric response spectra reveal spatial anisotropy and a red shift for all optical properties for Gd content up to 37.5%, which, coupled with the electronic structure results show how Gd alloying may be used to tune Ga2O3 without signif-icantly modifying the band edge contributions.