First-principle calculations of electronic and optical properties of Ti-doped β-Ga2O3 with intrinsic defects

The crystal structures, electronic structures and optical properties of Ti-doped beta-Ga2O3 with intrinsic defects are investigated by first-principle calculations based on density functional theory and the compensation effect between Ti dopant and intrinsic defects is discussed. Four defective structures of Ti-doped beta-Ga2O3 include TiGa2O3Oi (Ointerstitial), TiGa2O3Gai (Ga interstitial), TiGa2O3VO (O vacancy) and TiGa2O3VGa (Ga vacancy). The calculation results show that Ti dopant acts as an effective n-type dopant and makes the material more conductive. Besides, the defect formation energies of interstitial O and interstitial Ga are low under specific conditions, indicating that TiGa2O3Oi and TiGa2O3Gai are relatively stable. Interstitial O atom would compensate with Ti dopant and reduce the n-type conductivity of material, while interstitial Ga can enhance the n-type conduction of Ti-doped beta-Ga2O3. After Ti-doping, the intrinsic absorption edge shows a slight red-shift compared with intrinsic beta-Ga2O3. In addition, the optical absorption edge of defective structures (except TiGa2O3Gai) are red-shifted relative to Ti-doped beta-Ga2O3.