Polarization Analysis of Ga1-xAlxN and Zn1-xMgxO by First-Principles Calculation
Kazuto KOIKE, Takahiro AOKI, Syun IIDA, Yasuhito FUKUTA, Yasutomo UETSUJI, Shigehiko SASA, Masataka INOUE and Mitsuaki YANO
Abstract:Physical parameters of Ga1-xAlxN and Zn1-xMgxO 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 Zn0.5Mg0.5O/ZnO and O-polar ZnO/Zn0.5Mg0.5O as well as Ga-polar Ga0.5Al0.5N/GaN and N-polar GaN/Ga0.5Al0.5N 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. Key Words:ZnO, Zn1-xMgxO, GaN, Ga1-xAlxN, First-principles calculation, Spontaneous polarization, Piezoelectric polarization, Two-dimensional electron gas