INELASTIC LIGHT-SCATTERING FROM ELECTRONIC EXCITATIONS IN DEEP-ETCHEDQUANTUM DOTS AND WIRES

Resonant Raman spectroscopy of modulation-doped GaAs/AlGaAs multiple q uantum well dots and wires is reported. Deep etching with a SiCl4 reac tive ion etching process achieved an excellent aspect ratio (> 10:1) a nd low surface damage for dots and wires of sizes in the range 60-250 nm. A rich spectrum of single particle excitations was observed at Ram an shifts in the range 1-35 meV for both dots and wires. Sharp resonan ces were found for the Raman intensities. The electronic scattering in wires exhibits distinct polarization properties in agreement with the oretical predictions and the spin density excitation energies are in r easonable agreement with Hartree approximation calculations. The dispe rsion of the intrasubband plasmon collective mode in 60 nm wires has b een determined. The excitations in dots show a systematic shift to hig her energy with decreasing dot diameter consistent with increased conf inement. Magneto-Raman scattering from dot samples was also investigat ed at magnetic fields up to 12 T and the excitation spectra show level splitting, level crossing and mode softening with increasing magnetic field.