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 Sc_xAl_1−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 (Δ u 3 k) based on the layered hexagonal structure. [ABSTRACT FROM AUTHOR]