First-Principles Study on the Spontaneous Polarization of Wurtzite Zn1-ｘMgxO Alloy Crystals
Yasutomo UETSUJI, Eita NOMURA, Kazuto KOIKE, Shigehiko SASA, Masataka INOUE and Mitsuaki YANO
Abstract:Physical parameters of wurtzite Zn1-xMgxO (0 ≦ x ≦ 1) were analyzed using first-principles calculations. A plane-wave pseudopotential method was employed to a density functional theory, then the effect of Mg incorporation on its lattice parameters and spontaneous polarization in the c-axis direction was studied as a function of the Mg content x. Calculations showed only a little difference in the bond length while a considerable change in the bond angle by the replacement of the Zn atoms in Zn1-xMgxO with Mg atoms. Due to the atomic replacement, a linear decrease and increase with increasing x were brought about the c-axis and a-axis lengths, respectively, deducing an increase of the spontaneous polarization in the -c-axis direction. Cohesive energies of wurtzite and rocksalt Zn1-xMgxO were also calculated to compare the structural stability, and the former structure was shown to be more stable till the Mg content at around x = 0.5. Key Words:Urtzite Zn1-xMgxO alloy, First-principles calculation, Spontaneous polarization, Piezoelectric polarization, ZnO/Zn1-xMgxO heterostructure, Two-dimensional electron gas