Effects of oxygen vacancies on the structural and optical properties of β-Ga2O3

Abstract

The structural, electronic, and optical properties of β-Ga2O3 with oxygen vacancies are studied by employing first-principles calculations based on density function theory. Based on the defects formation energies, we conclude the oxygen vacancies are most stable in their fully charge states. The electronic structures and optical properties of β-Ga2O3 are calculated by Generalized Gradient Approximation + U formalisms with the Hubbard U parameters set 7.0 eV and 8.5 eV for Ga and O ions, respectively. The calculated bandgap is 4.92 eV, which is consistent with the experimental value. The static real dielectric constants of the defective structures are increased compared with the intrinsic one, which is attributed to the level caused by the Ga-4s states in the bandgap. Extra peaks are introduced in the absorption spectra, which are related to Ga-4s and O-2p states. Experimentally, β-Ga2O3 films are deposited under different O2 volume percentage with ratio-frequency magnetron sputtering method. The measured results indicate that oxygen vacancies can induce extra emission peaks in the photoluminescence spectrum, the location of these peaks are close to the calculated results. Extra O2 can increase the formation energies of oxygen vacancies and thus reduce oxygen vacancies in β-Ga2O3.

Deep level defects in Ge-doped (010) β-Ga2O3 layers grown by plasma-assisted molecular beam epitaxy

“…To date, there have been some theoretical calculations that predict states near these energy values based on the various oxygen and gallium vacancy related defects of several charge states and configurations but more work must be carried out in conjunction with careful experiments to elucidate further. 16,42,[45][46][47] The remaining states at E C À 1.27 eV (detected in trace amounts by DLOS), and the set of levels at E C À 0.18 eV À 0.21 eV found by DLTS, were not seen in the earlier EFG studied material. The role of vastly different growth methods, or the use of a different dopant could be responsible for these differences, and this would not be surprising.…”

“…Theoretical calculations have predicted the presence of vacancy-related energy levels near E C À 0.8 eV, though there is some controversy regarding the specific vacancy type (oxygen or gallium) in those works. 16,45,46 If indeed this is a vacancy-related state, it would not be surprising given that the different thermodynamic conditions of PAMBE vs. melt-based bulk crystal growth would generate different types and concentrations of Ga and O vacancies. However, a recent study has theoretically predicted that Fe Ga substitutional impurities can also manifest as a state near E C À 0.8 eV, and indeed an experimental correlation between the Fe concentration and the concentration of this trap within bulk substrate materials was observed along with an insensitivity to high energy particle irradiation that corroborates an extrinsic source.…”

Interaction between hydrogen and gallium vacancies in β-Ga2O3

“…21 B3LYPRef. 22 GGA + URefs 7,23,24 Experimenta(Å)12.3412.2512.3412.5512.23 ± 0.02b(Å)3.073.053.0353.083.04c(Å)5.865.845.7995.895.80β(deg)103.67103.9103.7103.67103.7, 103.83E g d (eV)4.864.874.694.924.9…”

Effect of cation vacancies on the optical and dielectric properties of KSr2Nb5O15: A first‐principles study

“…Figure shows the refraction and extinction coefficients of KSN, KSN‐K, KSN‐Sr, and KSN‐K&Sr In Figure A, the refraction for KSN is 2.082, KSN‐K is 3.843, KSN‐Sr is 4.529, and KSN‐K&Sr is 2.805. Compared with ε 1 ( ω ), the following relationship is satisfied:…”