Internal Transitions of Negatively Charged Excitons and Many-Electron Effects in GaAs Quantum Wells

States of charged magnetoexcitons in quasi-two-dimensional systems are investigated. The effect of excess electrons on internal transitions of negatively charged excitons X− in GaAs quantum wells is studied experimentally by optically detected resonance (ODR) spectroscopy and theoretically. An experimentally observed blue shift with excess electron density is explained in terms of collective excitations—magnetoplasmon bound to a mobile valence band hole. A possibility to observe photoluminescence of dark X− states in angle-resolved experiments is also discussed.