LOCAL EPITAXY OF SI SIGE WIRES AND DOTS

Local epitaxy through shadowing masks has been used to fabricate well- passivated SiGe quantum wells with lateral dimensions from 15 mu m dow n to 200 nm. The resulting SiGe mesas are investigated with convention al photoluminescence (PL) and spatially resolved PL. Using spatially r esolved PL, the luminescence of isolated single SiGe dots is observed for the first time. For mesa sizes below 1 mu m, the normalized intens ity increases with decreasing size and exceeds the reference signal by more than one order of magnitude for mesas grown through 200 nm wide windows. All investigated mesas show a pronounced blue shift compared to the reference areas. While the dependence of the blue shift on the mesa size is consistent with a very simple surface diffusion model, th e observed dependence on the growth temperature is more complicated an d not quite understood. Finally, the luminescence of a single 1 mu m w ide SiGe wire in dependence of the detected wire length after local ex citation is used to estimate the exciton density distribution along th e wire. A simple exponential decay fits the experimental data well wit h a decay length of about 10 mu m.