Binding Energy Of The Impurity State In A Strain GaN/Al_xGa_1-xN Cylindrical Quantum Dot Under The Pressure

Within the effective-mass approximation, the binding energy of a hydrogenic donor impurity state in a finite-potential GaN/AlxGa1-xN cylindrical quantum dot under the hydrostatic pressure is investigated via a variational approach.Firstly, within the effective-mass approximation, the binding energies as functions of the quantum dot height and radius, the impurity position, and the Al concentration are calculated by without considering the strain effect. Numerical results show that the binding energy are always monotonically decreasing with increasing radius, but increases as the height increases, reaches a maximum, and then decreases. When the impurity is located at the center of the quantum dot, the binding energy is maximum, and the increase of Al concentration can increase the binding energy.Then, we have considered the strong built-in electric field caused by the interface lattice mismatch and the influences of the strain effect on the physical parameters of the materials. Moreover, we also consider the hydrostatic pressure modifications of the strain. Numerical results show that the binding energy are always monotonically decreasing with increasing radius, but increases as the height increases, reaches a maximum, and then decreases, which is similar with the case that without strain. Moreover, the binding energy will be increased after considering the pressure. Via the calculation, we know that the built-in electric field caused by the strain will reduce the binding energy of the impurity state, and the influence is obvious when the quantum dot size is large, but the influence of strain on the parameters will increase the binding energy of impurity state, and the influence is obvious when the quantum dot size is small. moreover, because the increase of Al concentration can enhance the built-in electric field and the height of potential barrier, the binding energy of the impurity state increases with Al concentration increases, reaches a maximum, and then decreases.