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 width in ZnTe/GaAs and ZnSe/GaAs. The fabrication process relies on electron beam lithography and dry etching using a mixture of CH4/H2. We have extensively characterized the flat etched surfaces of both ZnTe and ZnSe using x-ray photoelectron spectroscopy (XPS), Raman scattering, and luminescence spectroscopy. Flat etched samples were also annealed. We found that improvements in the emission spectrum were related probably to defect removal in the as-grown samples and had a secondary impact in the etched and annealed samples. From XPS data, some evidence is found of zinc desorption from the surface, which is later corroborated 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 concentration in donors and acceptors and evidence of ZnTe/GaAs intermixing closer to the interface. No line broadening is observed and the emission 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.