Abstract

Semiconductor heterostructures display optical and electronic properties which are influenced by the dynamics of electronic excitations. The nature of the dynamical processes is sensitive to disorder due to nonideal growth conditions. Carrier localization is a new process which arises in the presence of disorder, and measurements have shown that at low temperature excitons in multiple quantum wells (MQW) are localized and that localization effects are responsible for their relaxation.^[1] We use resonant picosecond four-wavemixing (FWM) to probe the disorder induced effects near the bandedge of GaAs/AlGaAs MQW. The observed optical response suggests that two distinct classes of excitons are present, and that their contribution to the optical response can be separated based upon their polarization properties. The unique energy and temperature dependences of the two classes indicate that the two classes correspond to localized and delocalized excitons. Picosecond transient absorption experiments using circularly polarized light are employed to further examine the polarization properties of the excitonic optical response.

© 1992 IQEC