Effects of Submicron Confinement on Shallow Donors in GaAs-Ga1−xAlxAs Multiquantum well Structures

The nature of the free electronic states in GaAs-GaAlAs quantum well (QW) structures has been the subject of extensive investigation over the past few years and is by now relatively well understood. For a number of reasons, impurity states confined in QW structures are not as well understood, and not until very recently have experimental investigations been undertaken1. Variational calculations2–4 for Hydrogenic impurities are in general agreement in their predictions of substantial shifts in the energy levels of the impurities relative to the bulk values as the width of the QW approaches the effective Bohr radius of the impurities. The magnitude of the shifts depends on the width and depth of the QW, as well as the position of the impurity within the well.