EXCITONIC ENERGY-RANGE DIELECTRIC FUNCTION IN GAAS GA0.7AL0.3AS SINGLE QUANTUM-WELLS AT ROOM-TEMPERATURE

GaAs/Ga0.7Al0.3As single quantum-well heterostructures, grown by molec ular beam epitaxy, are investigated at room temperature using reflecta nce spectroscopy in the energy range 1.2-3.6 eV. The dielectric functi on of GaAs in the wells is deduced in the excitonic transition region around the GAMMA point of the Brillouin zone. The optical constants ar e determined on the basis of reflectance data using a Kramers-Kronig a nalysis, followed by an iterative technique of extraction applied to a multilayer scheme for the samples. The optical transitions, accuratel y located at the peaks of the absorption spectra, are compared to the transition energies calculated using the finite-square-well model in t he effective-mass approximation.