Surface polaronic effect on donor-impurity states of a wurtzite nitride nanowire: Two-parameter variational approach

Abstract

By employing the two-parameter variational approach, the donor-impurity states with surface optical (SO) phonons, also called SO phonon bound polarons in a quasi-one-dimensional (Q1D) wurtzite nanowire (NW) are investigated. Numerical calculations on a GaN NW are performed. The results reveal that the SO phonon contribution to the binding energy of the SO phonon bound polaron in GaN NWs reaches 200 meV, which is one order of magnitude larger than that of GaAs NWs with the same radius. The large contribution of SO phonons to the total binding energy is mainly ascribed to the stronger electron-phonon coupling constant in GaN materials. The calculated results of impurity binding energy are consistent with the recent experimental measurement of the active energy in GaN NW systems. The numerical results also shows that the two-parameter variational approach is necessary and suitable for the description of donor-impurity states in Q1D wurtzite GaN NW structures, especial for the NWs with a relatively small radius (such as R < 10 nm).