G. Finkelstein et al., OPTICAL SPECTROSCOPY OF NEUTRAL AND CHARGED EXCITONS IN GAAS ALGAAS QUANTUM-WELLS IN HIGH MAGNETIC-FIELDS/, Surface science, 362(1-3), 1996, pp. 357-362
We implement optical spectroscopy to study charged excitons in modulat
ion-doped GaAs/AlGaAs quantum wells. We report the first observation o
f the positively charged exciton and of the triplet state of the negat
ively charged exciton. Applying a gate voltage at high magnetic fields
, we investigate the transition between metallic and insulating states
. We find that while the photoluminescence line of the metallic two-di
mensional electron gas transforms smoothly into a negatively charged e
xciton, the Zeeman splitting of this line exhibits an abrupt change at
the metal-insulator transition.