OBSERVATION OF INTERNAL TRANSITIONS OF CONFINED EXCITONS IN GAAS ALGAAS QUANTUM-WELLS/

Internal transitions of confined hydrogenic excitons in type-I multipl e-quantum-well structures have been observed and studied as a function of magnetic field (0-15 T) and quantum well width (80-200 Angstrom). A highly sensitive technique that combines visible and far infrared me thods, optically detected resonance spectroscopy, was employed, and re vealed several internal excitonic transitions, with the 1s --> 2p(+) t ransition dominant. The energies of the 1s --> 2p(+) transition vs mag netic field are in very good agreement with variational calculations f or the 80 and 125 Angstrom wells. The strength of the intraexcitonic f eatures was observed to be much weaker in the 200 Angstrom well-width samples.