Inter-band transition Absorption peaks 1 Ca-doped α-Ga2O3 1 Calcium 1 Charge density distributions 1 Complex dielectric functions 1 Continuous media 1 Density functional theory 1 Dielectric medium 1 Effective energy 1 Electric losses 1 Electric potential 1 Electrical measurement 1 Electrically actives 1 Electron-beam 1 Electron-hole generation 1 Electronic structure 1 Electronic structure and optical properties 1 Electrons 1 Ellipsometry 1 Ellipsometry measurements 1 Energy gap 1 Ferromagnetic materials 1 Ferromagnetism 1 First-principles 1 First-principles study 1 Free path 1 General trends 1 Generalized gradient approximations 1 Generation rate 1