NANOMETER FABRICATION TECHNIQUES FOR WIDE-GAP II-VI SEMICONDUCTORS AND THEIR OPTICAL CHARACTERIZATION

We have fabricated dots and wires down to 30 nm diameter and 60 nm wid th in ZnTe/GaAs and ZnSe/GaAs. The fabrication process relies on elect ron beam lithography and dry etching using a mixture of CH4/H2. We hav e extensively characterized the flat etched surfaces of both ZnTe and ZnSe using x-ray photoelectron spectroscopy (XPS), Raman scattering, a nd luminescence spectroscopy. Flat etched samples were also annealed. We found that improvements in the emission spectrum were related proba bly to defect removal in the as-grown samples and had a secondary impa ct in the etched and annealed samples. From XPS data, some evidence is found of zinc desorption from the surface, which is later corroborate d by Raman scattering in etched wires with the appearance of tellurium modes. The luminescence spectra of flat etched samples show no major changes in the spectral lines, with a hint of a change in relative con centration in donors and acceptors and evidence of ZnTe/GaAs intermixi ng closer to the interface. No line broadening is observed and the emi ssion intensity is retained. The emission and Raman scattering spectra of etched wires and dots confirms that negligible fabrication damage is incurred as well as the absence of further strain or strain release after etching.