Comparative study of the fundamental properties of Ga2O3 polymorphs

Full potential linearized augmented plane wave method plus local orbitals (FP-LAPW thorn lo) on the basis of Density Functional Theory (DFT) is called to study the structural, electronic, elastic, optical, thermodynamic and transport properties of four different phases of Ga2O3 denoted by alpha, beta, delta, and epsilon. The calculated gap energy Eg for the stable polymorph beta-Ga2O3 using the modified Becke-Johnson (mBJ) exchange potential is 4.6 eV which lies in the deep ultraviolet range making Ga2O3 promising for optoelectronics. Thermal effects on some macroscopic properties such as heat capacity, thermal expansion coefficient, Gruneisen parameter and Debye temperature are predicted using the quasi-harmonic Debye model. The analysis of transport properties for beta-Ga2O3 using semi-classical Boltzmann transport theory in temperature range between 300 and 1000 K showed high Seebeck coefficient S = -348.4 mu VK-1 at room temperature with huge power factor PF = 39.5 x 10(10) WK(-2)m(-1) s(-1) at T = 1000 K. This suggests that Ga2O3 is a potential thermoelectric material.