Effects of strain on the optical and thermodynamic properties of β-Ga2O3

Abstract

Elastic and thermodynamic properties of β-Ga2O3 are studied from first-principles calculations in both the local density approximation (LDA) and generalized gradient approximation (GGA) within the density functional theory (DFT) framework. Temperature-dependent elastic stiffness constants (Cij) are computed in the quasi-static approximation using the calculated thermal expansion coefficients (TECs) that are found to contain significant anisotropy consistent with the monoclinic lattice structure. Values for elastic moduli, Debye temperature, and sound velocities along crystallographic directions are then computed using the Cij. Additionally, thermal expansion has been calculated in the quasi-harmonic approximation and compares well with recent measurements. The dielectric function and its variation with applied shearing strains is also presented as determined by the Drude-Lorentz model. Finally, the photoelastic tensor was calculated and the predicted acousto-optic figure of merit is presented.