Binding energies of shallow impurities in asymmetric strained wurtzite Al_xGa_1−xN/GaN/Al_yGa_1−yN quantum wells

Abstract

The ground state binding energies of hydrogenic impurities in strained wurtzite Al x Ga 1 x N/GaN/Al y Ga 1 y N quantum wells are calculated numerically by a variational method. The dependence of the binding energy on well width, impurity location and Al concentrations of the left and right barriers is discussed, including the effect of the built-in electric field induced by spontaneous and piezoelectric polarizations. The results show that the change in binding energy with well width is more sensitive to the impurity position and barrier heights than the barrier widths, especially in asymmetric well structures where the barrier widths and/or barrier heights differ. The binding energy as a function of the impurity position in symmetric and asymmetric structures behaves like a map of the spatial distribution of the ground state wave function of the electron. It is also found that the influence on the binding energy from the Al concentration of the left barrier is more obvious than that of the right barrier.