Exciton dynamics for extended monolayer islands in thin ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/InP quantum wells

The exciton dynamics for extended monolayer islands in thin growth-interrupted ${\mathrm{In}}_{0.53}$${\mathrm{Ga}}_{0.47}$As/InP quantum wells is investigated with use of temperature-dependent and time-resolved photoluminescence spectroscopy. Three different temperature regimes are found. At temperatures below 40 K, no coupling between neighboring islands is observed, indicating exciton localization at potential fluctuations at the interface. Increasing the temperature causes exciton delocalization and the decay of excitonic luminescence is influenced by the exciton transfer between the islands. At temperatures above 130 K, the islands are strongly coupled and the transfer occurs within our time resolution of about 50 ps. A model is developed to describe the exciton transfer quantitatively. We are thus able to determine the exciton mobility to values up to 150 ${\mathrm{cm}}^2$/V s for an effective well width of 2 monolayers (≃0.6 nm). Analyzing our experimental results theoretically, we conclude that, at low temperatures, inelastic scattering—and, therefore, exciton localization—is dominant. This result is confirmed by the nearly temperature-independent excitonic lifetime in this temperature region. At higher temperatures, however, the excitons become delocalized and we show, by comparison with theory, that the mobility is controlled by interface roughness scattering.