Effect of Thin Film Thickness on the Electronic Properties of Wurtzite Structure (ZnO and GaN): A Density Functional Theory Study

By using first-principle density-functional theory (DFT) calculations supplemented with symmetry analysis, we investigated the effect of thin-film thickness on the electronic properties of non-polar ( ZnO-wz and GaN-wz. We find that the electronic band structures of thin-film non-polar ( surface with layer variations from two until ten bilayers show the Rashba spin splitting. Importantly, we revealed that this splitting is found to be strongly anisotropic observed in the valence band maximum (VBM) around the Γ point. We clarified the origin of the anisotropic spin splitting in the electronic band structures by considering the point-group symmetry (PGS) of the present system. We found that the changes of the PGS from C 6v (for polar [0001] direction) to C s (for non-polar ( direction) are responsible for inducing the anisotropic of the spin splitting. To further confirm the anisotropic splitting, we calculated the Rashba spin splitting parameters for different directions of the k -path. We found that these parameters are different in magnitude for a different direction of the k -path indicating the anisotropic spin splitting quantitatively, which is consistent well with symmetry analysis. Finally, we conclude that the observed Rashba spin splitting in the wurtzite surface structure is promising for spintronics applications.