Well-width dependence of exciton-phonon scattering in In x Ga 1 2 x As / GaAs single quantum wells

The temperature and density dependencies of the exciton dephasing time in In 0.18Ga0.82As/GaAs single quantum wells with different thicknesses have been measured by degenerate four-wave mixing. The excitonphonon scattering contribution to the dephasing is isolated by extrapolating the dephasing rate to zero-exciton density. From the temperature dependence of this rate we have deduced the linewidth broadening coefficients for acoustic and optical phonons. We find acoustic-phonon coefficients that increase from 1.6 to 3 meV/K when increasing the well width from 1 to 4 nm. This is in quantitative agreement with theoretical predictions when the spatial extension of the exciton wave function, strongly penetrating into the GaAs barrier in thin InxGa12xAs quantum wells, is taken into account. The optical-phonon coefficient does not show a systematic dependence on well thickness, and is comparable with the value for bulk GaAs. @S0163-1829 ~99!02103-7#