Dephasing Processes in Self-Organized Strained InGaAs Single-Dots on (311)B-GaAs Substrate

Single-dot photoluminescence measurements are undertaken on a number of individual InGaAs disks spontaneously formed on the GaAs-(311)B face. Well-isolated distinctive narrow single-dot luminescence lines, the narrowest of which is 34 µ eV in FWHM, is measured using a microscope and their evolution with excitation density is examined. Under very low excitation, individual dot luminescence is well approximated by the Lorentzian lineshape. Excitation via the barrier continuum results in very low luminescence saturation density and simultaneous broadening into a non-Lorentzian lineshape. In contrast, excitation resonant with excited states, causes no such broadening, but saturation power is about three orders of magnitude larger than under barrier excitation. Such phenomena are explained by different carrier flows into the dot states. Carrier-carrier scattering is discussed as a primary dephasing process that causes line broadening.