First-principles calculations of spontaneous polarization in ScAlN

The aim of this study is to obtain a systematic insight into the scandium (Sc) concentration dependence of the spontaneous polarization (P-sp) in ScxAl1-xN by using first-principles calculations. From the calculated results, we observe that a structural change from a c-axis polarized wurtzite structure to a nonpolarized layered hexagonal structure takes place at x = 0.67, and the spontaneous polarization decreases nonlinearly with a change in the Sc concentration. Furthermore, we calculate the spontaneous polarizations from each cation individually and find that the spontaneous polarization from aluminum-nitrogen (Al-N) (P-sp(AlN)) is higher than that from scandium-nitrogen (Sc-N) (P-sp(ScN)). This difference in spontaneous polarization arising from the cationic origin is attributed to the difference in the internal parameter along the c axis (Delta u(3)(k)) based on the layered hexagonal structure.

Automated summary

This study systematically investigates the effect of scandium concentration on spontaneous polarization in ScxAl1-xN using first-principles calculations. It is found that a structural transition from a c-axis polarized wurtzite structure to a nonpolarized layered hexagonal structure occurs at x = 0.67, leading to a nonlinear decrease in spontaneous polarization. Additionally, the comparison of spontaneous polarizations from different cations reveals a higher value for aluminum-nitrogen (Al-N) compared to scandium-nitrogen (Sc-N) due to differences in internal parameters along the c axis in the layered hexagonal structure.