Piezoelectric properties of Ga₂O₃: a first-principle study

Abstract

The compounds exhibit piezoelectricity, which demands to break inversion symmetry, and then to be a semiconductor. For Ga₂O₃, the orthorhombic case (ϵ-Ga₂O₃) of common five phases breaks inversion symmetry. Here, the piezoelectric tensor of ϵ-Ga₂O₃ is reported by using density functional perturbation theory (DFPT). To confirm semiconducting property of ϵ-Ga₂O₃, its electronic structures are studied by using generalized gradient approximation (GGA) and Tran and Blaha’s modified Becke and Johnson (mBJ) exchange potential. The gap value of 4.66 eV is predicted with mBJ method, along with the effective mass tensor for electron at the conduction band minimum (CBM) [about 0.24 m₀]. The mBJ gap is very close to the available experimental value. The elastic tensor C_ij are calculated by using the finite difference method (FDM), and piezoelectric stress tensor e_ij are attained by DFPT, and then piezoelectric strain tensor d_ij are calculated from C_ij and e_ij. In this process, average mechanical properties of ϵ-Ga₂O₃ are estimated, such as bulk modulus, Shear modulus, Young’s modulus and so on. The calculated d_ij are comparable and even higher than commonly used piezoelectric materials such as α-quartz, ZnO, AlN and GaN.

Graphical abstract