First-principles study on point defect behaviors and electronic structures of Mg-doping β -Ga 2 O 3

Mg is generally recognized as a potential impurity for achieving p-type doping in β -Ga 2 O 3 , but the point defects severely restrict the realization of efficient p-type conductivity. To explore the formation mechanism of point defects, first-principles were utilized to elucidate the characteristics of Mg-doping point defects in β -Ga 2 O 3 . The formation energy and transition level results indicate that Mg Ga1 (Mg antisite Ga 1 ) and Mg Ga1 - V O1 (Mg antisite Ga 1 and vacancy O) exhibit deep acceptor characteristics. The charge density difference confirms the ionic nature of Mg–O bonds in β -Ga 2 O 3 with Mg Ga1 , Mg Ga1 - V O1 , and Mg Ga2 - V O1 (Mg antisite Ga 2 and vacancy O), and reveals that the Mg atom loses electrons while the surrounding O atoms gain electrons in β -Ga 2 O 3 . Crystal orbital Hamiltonian populations demonstrates that Mg atom in Mg Ga1 and Mg Ga2 (Mg antisite Ga 2 ) both form ionic bonds with trigonally O 1 , which possess the minimum bond strength among all relevant bonding configurations. The electronic structure calculations based on the GGA + U method reveal that the introduction of Mg Ga1 , Mg Ga1 - V O1 , and Mg Ga2 - V O1 all induces a level within the bandgap. Specifically, the level introduced by Mg Ga1 is primarily contributed by O-2p orbitals while that of Mg Ga1 - V O1 and Mg Ga2 - V O1 are mainly originated from Ga-4p orbitals. Furthermore, the analysis of the phonon spectra and binding energy indicates that Mg Ga1 and Mg Ga2 - V O1 are relatively stable, while Mg Ga1 - V O1 is unstable in β -Ga 2 O 3 . The microscopic physical mechanisms of Mg-doping point defects in β -Ga 2 O 3 at the atomic scale are analyzed, providing a theoretical basis and guidance for achieving high quality p-type doping.