Ca-doped α-Ga2O3 1 Calcium 1 Charge density distributions 1 Complex dielectric functions 1 Density functional theory 1 Electronic structure 1 Electronic structure and optical properties 1 Energy gap 1 First-principles 1 First-principles study 1 Generalized gradient approximations 1 High-power transistors 1 Inter-band transition 1 Light 1 Optical properties 1 Plane-wave pseudopotential method 1 Pure α-Ga2O3 1 Semiconducting gallium compounds 1 Semiconductor doping 1 Valence bands 1 Wide band gap semiconductors 1