Influence of surface optical phonon on the electronic surface states in wurtzite group-III nitride ternary mixed crystals

An intermediate-coupling variational method is presented to investigate the surface electron states in wurtzite A x B 1− x N (A, B=Al, Ga and In) ternary mixed crystals (TMCs). Corresponding effective Hamiltonian are derived by considering the surface-optical-phonon (SO-phonon) influence and anisotropic structural effect. The surface-state energies of electron, the coupling constants and the average penetrating depths of the electronic surface-state wave functions have been numerical computed as a function of the composition x and the surface potential V 0 for the wurtzite Al x Ga 1− x N, Al x In 1− x N and In x Ga 1− x N, respectively. The results show that the surface-state levels of electron are reduced with the increasing of the composition x in wurtzite A x B 1− x N. It is also found that the electron-surface-optical-phonon (e-SO-p) coupling lowers the surface-state energies of electron and the shifts of the electronic surface-state energy level in the wurtzite Al x Ga 1− x N and Al x In 1− x N increase with the increasing of the composition x . However, in the wurtzite In x Ga 1− x N, the case is contrary. The influence of the e-SO-p interaction on the surface electron states can not be neglected in wurtzite A x B 1− x N.