Spectroscopy of Charged Donors and Many-Electron Effects in Semiconductor Quantum Wells |
| B.D. McCombe, Z.X. Jiang, J.G. Tischler, B.A. Weinstein Department of Physics and Center for Advanced Photonic and Electronic Materials, SUNY at Buffalo, Buffalo, NY 14260, USA and P. Hawrylak Institute for Microstructural Sciences, NRC, Ottawa, Canada K1A OR6 |
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| Far infrared magnetospectroscopic studies of negative donor ions (D-), and donors in the presence of many excess electrons in high magnetic fields in GaAs/AlGaAs quantum wells are reviewed. Both singlet and triplet transitions of well-center D-ions were observed and are in good agreement with recent theoretical calculations. For off-well-center D-ions evidence for a predicted magnetic-field-induced "unbinding" of the second electron was found. In the presence of many excess electrons the D-singlet and -triplet transitions are blue-shifted substantially and evolve into bound magnetoplasmon excitations. Cusps are observed at integral and fractional Landau-level filling factors (ν) in a plot of normalized blue-shift of the D-singlet-like bound magnetoplasmon transition vs. ν. For ν&<1, the singlet-like bound magnetoplasmon transition continuously approaches the isolated D-singlet transition with increasing magnetic field, while the triplet-like transition loses strength, irrespective of the electron density. Exact diagonalization studies of a donor ion with a few electrons in a parabolic lateral confining potential show the importance of electron-electron interactions and localization due to the long-range fluctuating potential in explaining this behavior. High pressure studies in a specially designed diamond anvil cell exhibit a continuous evolution from bound magnetoplasmon transitions to isolated D-transitions to neutral donor transitions in a single sample as the pressure is increased and the electron density in the wells is decreased. |
| DOI: 10.12693/APhysPolA.96.559 PACS numbers: 73.20.Dx, 73.20.Hb, 78.66.Fd |