The influence of built-in electric field on binding energy of bound polaron and polaron effects in wurtzite ZnO/MgxZn1−xO quantum well

The influence of the built-in electric field on the binding energy of a bound polaron and the polaron effect in a wurtzite ZnO/MgxZn1−xO quantum well are studied using the improved Lee-Low-Pines intermediate coupling method. The ground-state binding energy, the contributions from different branches of optical phonons to the energy and the binding energy are presented as the functions of well width, impurity position and composition. In the numerical calculations, the anisotropic properties of the frequencies of the different branches of optical phonons, electron effective mass, dielectric constant, the electron-optical phonon interaction and the impurity center-optical phonon interaction are considered. The results show that the built-in electric field has obvious influence on the energy, the binding energy and the polaron effect, and it affects the contributions of different phonon modes to the energy and the binding energy with different degrees. The built-in electric field significantly increases the total phonon contribution to the energy, but it reduces the total phonon contribution to the binding energy. The binding energy of the bound polaron with the built-in electric field is less than that without the built-in electric field, and it declines rapidly with increasing well width. Because of the built-in electric field effects, the contributions from different branches of phonons to the energy and the binding energy and the functions of binding energy with well width and impurity center position are different from the cases without the built-in electric field. The built-in electric field in the wurtzite ZnO/MgxZn1−xO quantum wells has a great impact on the binding energy and polaron effect, and the polaron effect in the wurtzite ZnO/MgxZn1−xO quantum wells is significantly greater than that in the zinc blende GaAs/AlxGa1−xAs QWs, hence, it is necessary to discuss the built-in electric field and polaron effect when considering the problem of electronic state in such systems.