Far infrared excitations of shallow donor impurities in gaas/algaas multiple quantum well heterostructures

The effects of confinement of impurities (acceptors and donors) in semiconductors of reduced dimensionality been the focus of much recent theoretical (1) and experimental (2) attention. In the present work, far infrared (FIR) and resonant Raman scattering (RRS) experiments have been performed on MBE-grown GaAs/AlGaAs multiple quantum well heterostructures that were selectively doped with Si donors in the centers of the quantum well and barrier layers. Motivations for these investigations include a need to obtain information on the binding of electrons in the well to positively charged impurities in the barriers and to examine in detail the effects of the screening of the Coulomb interaction by free carriers in this quasi two-dimensional system. Representative results of these studies are highlighted below.