Electronic structure and properties of trapped holes in crystalline and amorphous Ga 2 O 3

Structure and electronic properties of self-trapped holes were studied in both crystalline and amorphous Ga 2 O 3 using density functional theory (DFT) and the nonlocal PBE0-TC-LRC density functional. Amorphous (a) Ga 2 O 3 structures were generated using classical molecular dynamics and the melt-quench technique and further optimized using DFT. They exhibit an average density of 4.84 g / cm 3 and band gap around 4.3 eV. Calculations predict deep hole trapping in crystalline and amorphous phases with the hole-trapping energies in the amorphous structures being deeper than those found in the crystalline structure. In a − Ga 2 O 3 , trapped holes are localized around low-coordinated oxygen atoms (two or three coordinated). We predict the formation of stable hole bipolarons in both the crystalline and amorphous phases facilitated by the formation of O–O bonds with binding energies about 0.2 eV.