Binding energies and oscillator strengths of impurity states in wurtzite InGaN/GaN staggered quantum wells

摘要

Using the variational methods, we have calculated the binding energies of the lowest donor states, Is and 2p_±, in wurtzite InGaN/GaN staggered quantum wells. The binding energies in narrow wells are larger in magnitude than the values in bulk GaN due to the quantum confinement effects. However, the energies decrease sharply in wider wells because of the weakening confinement due to the strong built-in electric field inside the well. The binding energies of donors placed at the opposite edges of the well are quite different as the built-in electric field forms an asymmetric, triangular potential inside the well. The oscillator strength of the possible transitions between the donor states is then computed by modelling them as the states of a two-level atom. A magnetic field applied along the growth direction splits up the degenerate 2p_± states. The amount of splitting in the quantum well is found to be small possibly due to the heavy electron effective mass inside the well. The oscillator strength of the transition between the donor states becomes greater with the increasing magnetic field.