OPTICAL-ABSORPTION STUDIES OF THE EXCITONIC LINEWIDTH IN GAAS/GA0.73AL0.27AS MULTIPLE QUANTUM-WELL STRUCTURE

In this work we present results of normal incidence reflectance applied to superlattice (SL) molecular beam epitaxy (MBE) grown samples. An overview of some principles of the technique, the experimental apparatus, the measuring method and data reduction are also included. Performing a detailed analysis of the QWs optical absorption line shapes as well of the peak exciton positions as a function of the sample temperature, we obtain a direct evaluation of the interaction between the quantum wells (QWs) states and the lattice vibrations. The obtained results are then analyzed and compared with current electron-phonon (e-ph) schemes. In particular, for a sample containing ten 53 angstrom thick GaAs QWs, separated by 53 angstrom thick Al0.27Ga0.73As barriers, the E1hh 1s exciton peak shows an interaction with acoustical phonons of hBAR-omega almost-equal-to 20.8 meV, nearly the same value as evaluated for the GaAs bulk gap. The broadening of the same peak is dominated by a superlattice longitudinal-optical (LO) phonon mode for which hBAR-omega almost-equal-to 34.9 meV.