Polarization Analysis of Ga_1-xAl_xN and Zn_1-xMg_xO by First-Principles Calculation

Abstract

Physical parameters of Ga_1-xAl_xN and Zn_1-xMg_xO wurtzite crystals (x = 0 and 0.5) were analyzed using first-principles calculation. A plane-wave pseudopotential method was employed to a density functional theory, and the effect of alloying on the lattice parameters, spontaneous polarization in the c-axis direction, elastic stiffness and piezoelectric stress constants were calculated. Polarization effect in the heterosystems of Zn-polar Zn_0.5Mg_0.5O/ZnO and O-polar ZnO/Zn_0.5Mg_0.5O as well as Ga-polar Ga_0.5Al_0.5N/GaN and N-polar GaN/Ga_0.5Al_0.5N was compared by estimating their interface charges. The interface charges of the former two systems were estimated to be ∼5 times larger than those of the latter two assuming the strained structures by pseudomorphic growth.