Abstract

In two-dimensional GaAs/GaAlAs quantum well structures, heavy-hole exeitons have exhibited strong inhomogeneous broadening at low temperatures by interface roughness.¹ The roughness can scatter mobile excitons elastieally and provides a range in energy for exciton states among which inelastic scattering can occur by acoustie phonons. At low temperature a sharp changeover in energy at the center of the inhomogeneous exciton line has been observed between the strongly localized states and states delocalized over a scale of 1 μm.¹ The inelastic scattering rates were found to depend strongly on whether the exeitons were localized or mobile, being an order of magnitude greater for the latter. The scattering rate and hence the the localization properties are expected to depend strongly on the amuont of disorder. Photon echo measurements on GaAs quantum wells with extremely flat interfaces², and hence a small amount of disorder, yielded elastic scattering rates consistent with all the exeitons being mobile. The opposite effect of increased disorder should lead eventually to localization of all states. This has not been measured in 2-d quantum well systems to date.

© 1988 Optical Society of America