DETERMINATION OF EXCITONIC PROPERTIES IN GAAS GA1-XALXAS QUANTUM-WELLS BY OPTICAL WAVE-GUIDING EXPERIMENTS/

The absorption of single GaAs quantum wells in Ga1-xAlxAs or GaAs/AlAs short-period superlattices is studied in optical waveguiding experime nts at low and at room temperatures. We show that a complete character ization and determination of the guide parameters is essential in orde r to determine accurately the optical properties of quantum wells or s uperlattices embedded in the guide. The waveguiding configuration allo ws us to obtain the quantum well absolute absorption coefficients in b oth polarization directions, parallel and perpendicular to the plane o f the layers, and to determine the exciton binding energies and the as sociated oscillator strengths. New results are presented for an enlarg ed quantum well in a superlattice. We show that the excitonic binding energies depend on the extension of the wavefunction in the superlatti ce and are different for heavy- and light-hole excitons. The experimen tal values obtained for a quantum well in an alloy agree well with rec ent theoretical calculations.