Shallow impurities in quasi-two-dimensional systems: D0 and D− states

Abstract The electronic properties of two-electron shallow impurities (D- centers) in GaAs/AlGaAs multiple-quantum-well structures have been studied via far-infrared magneto-spectroscopy. Several experimental results are reported: the electron occupation of the shallow donor states at low temperature, temperature dependence of the occupancy, many-electron effects and resonant polaron interactions. Comparison with the neutral donor (D0) states is made.