Abstract

Heavy hole excitons in GaAs/AlGaAs multiple quantum well structures can be localized by potential fluctuations due to interface roughness and alloy disorder. Localized excitons can either tunnel to other localized sites accompanied by absorption or emission of acoustic phonons or be thermally activated to delocalized exciton states with higher energy.¹ In contrast, the dynamics of delocalized excitons are determined by acoustic phonon scattering on the exciton dispersion curve and elastic scattering by potential fluctuations.¹ As a result, in the transition region between localized and delocalized exciton. states the relaxation rate of excitons is expected to depend strongly on the exciton energy. Using new methods of high resolution nonlinear laser spectroscopy,² we have been able to measure exciton relaxation rates at a given energy and reduce complications encountered in time domain methods where pulse band- widths may be of the order of the width of the transition region.

© 1990 Optical Society of America