MAGNETO-RAMAN RESONANCES IN QUANTUM-WELLS - EXCITONIC EFFECTS

We have measured Raman resonance profiles in GaAs/AlAs multiple quantu m wells under magnetic fields up to 20 T for both (100) and (111) crys tal orientations. The results are interpreted as double Raman resonanc es involving magneto-excitons as intermediate states in the scattering process. A theoretical model including excitonic effects reproduces r emarkably well the main features of the observed double Raman resonanc es. Our work clarifies the essential role of excitons in the resonant behavior of the Raman cross-section in low-dimensional semiconductors.