EXCITON-POLARITON BEHAVIOR OF THE ABSORPTION-EDGE OF THIN GAAS CRYSTALS WITH THE SUPER-QUANTUM THICKNESS AND MQW ENLARGED BARRIERS

At T = 1.7 K the optical absorption of pure GaAs samples with thicknes s d = 0.4 to 4.4 mu m has been investigated in the region of the excit on-polariton resonances. The dependence of the integral absorption on the thickness is considered as a result of the competition of the opti cal processes in two different sample regions: near-surface region, wh ere the integral absorption saturates due to increasing damping parame ter in the electric field and central region, where the exciton-polari ton is not perturbed. We have observed a series of narrow lines near t he ground GaAs exciton state in the part of MQW spectra which belongs to the enlarged barrier. Calculations by the transfer matrix method gi ve a good agreement with the model taking into account the quantizatio n of the exciton as a whole and exciton-polariton wave interference.