Well-width dependence of exciton-phonon scattering in InxGa1-xAs/GaAs single quantum wells

The temperature and density dependencies of the exciton dephasing time in I n0.18Ga0.82As/GaAs single quantum wells with different thicknesses have bee n measured by degenerate four-wave mixing; The exciton-phonon scattering co ntribution to the dephasing is isolated by extrapolating the dephasing rate to zero-exciton density. From the temperature dependence of this rate we h ave deduced the linewidth broadening coefficients for acoustic and optical phonons. We find acoustic-phonon coefficients that increase from 1.6 to 3 m u eV/K when increasing the well width from 1 to 4 nm. This is in quantitati ve agreement with theoretical predictions when the spatial extension of the exciton wave function, strongly penetrating into the GaAs barrier in thin InxGa1-xAs quantum wells, is taken into account. The optical-phonon coeffic ient does not show a systematic dependence on well thickness, and is compar able with the value for bulk GaAs. [S0163-1829(99)02103-7].