RAPID CARRIER RELAXATION IN IN0.4GA0.6AS GAAS QUANTUM DOTS CHARACTERIZED BY DIFFERENTIAL TRANSMISSION SPECTROSCOPY/

Carrier relaxation in self-organized In0.4Ga0.6As/GaAs quantum dots is investigated by time-resolved differential transmission measurements. The dots have a base dimension of around 14 nm and a height of 7 nm, leading to an average energy separation of the ground and first excite d electronic states much greater than the LO-phonon energy, so the pho non-mediated electron relaxation is expected to be slow. Our measureme nts indicate that, even at low carrier densities (less than one electr on-hole pair per dot), the electron and hole relaxation time constants are 5.2 and 0.6 ps, respectively; this indicates a lack of any ''phon on bottleneck'' and is consistent with a model of electrons scattering from holes which can relax rapidly via phonon emission. [S0163-1829(9 8)52716-6].