Energetics and migration of point defects inGa2O3

Abstract

The results of a theoretical study on the point defects of monoclinic ␤-Ga 2 O 3 are reported here. The point defects considered here are vacancies, interstitials together with dopant ions such as Be, Mg, In, Cr, Si, Ge, Sn, and Zr. Since the low symmetry of the monoclinic lattice does not provide an unambiguous location of interstitial sites and migration paths, we propose a unique way for their identification in terms of the electron density topology. Special attention has also been given to the preference among the lattice and interstitial sites for the impurity defects, and its explanation in terms of structural, electrostatic, and electron density arguments. The calculated results find the most prominent features in the lattice to be the existence of ͑i͒ empty channels along the b direction, and ͑ii͒ atomic layers perpendicular to them. Their interplay governs the stability and mobility of the point defects in ␤-Ga 2 O 3. The anionic Frenkel pair consisting of the oxygen vacancy and oxygen interstitial is predicted to dominate the defect structure in the lattice. The dopants considered here are likely to be stabilized at the octahedral gallium sites, except for Be +2 , which prefers a tetrahedral gallium site in the lattice. Some of the possible migration paths have been determined, and the pseudoactivation energies for the intrinsic, oxygen-rich, and oxygen-deficient conditions are computed as a function of temperature. It is suggested that tuning the concentration of oxygen can lead to a change in the anisotropy of the ionic conductivity in ␤-Ga 2 O 3 .

Dispersion of Refractive Index of β-Ga2O3 Thin Films

“…The obtained values for the Ga ions were close to those for the ideal β-Ga 2 O 3 lattice. The slight deviations to the low side were most probably due to anion vacancies as an indispensable element of the actual β-Ga 2 O 3 lattice structure [25]. This was confi rmed for fi lms annealed in different atmospheres.…”

Polarization of optical spectra in transparent conductive oxide β‐Ga2O3

“…On the other hand, the electrical conductivity along the b axis was dominant. This difference suggests two processes of electrical conductivity: one is hopping of electrons between oxygen vacancies, and second is migration of interstitial oxygen ions along the b axis at high temperature [14].…”

Numerical Modelling of the Czochralski Growth of β-Ga2O3

“…RUS experiments were performed in the temperature range of 100 K to 1600 K. Currently, the spectra collected close to room temperature have been analysed, yielding (for better visualization, the symmetric lower half of the tensor has been left empty): For the purpose of comparison, we refer to our computations employing the software GULP [32], which contains a potential model with Coulomb interaction, Buckingham potential and core shell spring-like interactions. All parameters were taken from Blanco et al [23], who used a fitting with respect to the experimental lattice geometry, bulk modulus, and static and high-frequency dielectric constants. Please note that thermal energy is not included in this kind of calculation: The anisotropy of the computed elasticity tensor is similar to the experimentally observed anisotropy, e.g., c 22 > c 33 > c 11 and c 66 > c 55 > c 44 .…”