Hydrostatic Pressure And Screening Influence On Binding Energies Of Impurity In Quantum Wells Under An External Field

In this thesis, we consider the Influence of hydrostatic pressure and screening on theBinding Energies of impurity in Quantum Wells under an external magnetic field.First, considering the hydrostatic pressure and screening effect on the GaAs/AlxGa1-xAsand GaN/AlxGa1-xN quantum well with infinite barriers. A variational method underisotropic effective band mass approximation is used to numerical calculation the bindingenergies of the impurity in the two systems. In the calculation, the pressure effects on bandoffsets between channel and barrier materials, the electron effective mass and dielectricconstant are considered. The relations between the binding energies of donors with wellwidth and pressure are given. We also discussed the difference between the cases with andwithout screening. The result indicates that the binding energies increases with pressureand decreases with the well width. In our calculation range of pressure, the enhancementsof the donor binding energy for the given well width d=5nm and pressure P=2GPa,P=4GPa are about17.47%and35.42%in GaAs/AlxGa1-xAs quantum well. For the case ofGaN/AlxGa1-xN quantum well this value is smaller than in GaAs/AlxGa1-xAs quantum well,but cannot be neglected. Screening effect increases with pressure and decreases the bindingenergy of impurity states significantly.Furthermore, considering the hydrostatic pressure and screening effect on theGaN/AlxGa1-xN quantum well with infinite barriers under an external magnetic field. Thevariational method is used to numerical calculation the binding energies of the impurity inthe system. The relations between the binding energies of donors with magnetic field andwell width are given. We also discussed the difference between the cases with and withoutscreening. The result indicates that the binding energy increases with the well width undera fixed magnetic field and pressure. The result also shows that the binding energy increaseswith the magnetic field for a given well width and pressure. Because of the screeningreduce coulomb interaction effectively, the binding energy of impurity states decreasessignificantly. Screening effect increases with the pressure and decreases with the magneticfield.