Observation of Internal Transitions of Confined Excitons in GaAs/AlGaAs Quantum Wells

Internal transitions of confined hydrogenic excitons in type-I multiple-quantum-well structures have been observed and studied as a function of magnetic field (0–15 T) and quantum well width (80–200 Å). A highly sensitive technique that combines visible and far infrared methods, optically detected resonance spectroscopy, was employed, and revealed several internal excitonic transitions, with the $1s\to {2p}_{+}$ transition dominant. The energies of the $1s\to {2p}_{+}$ transition vs magnetic field are in very good agreement with variational calculations for the 80 and 125 Å wells. The strength of the intraexcitonic features was observed to be much weaker in the 200 Å well-width samples.