The spatially resolved optical emission properties of laterally overgrown GaN hexagonal pyramids on (111)Si substrates were investigated by using cathodoluminescence spectroscopy and mapping techniques. The results were compared with the structural properties deduced from scanning and transmission electron microscopic results. In order to elucidate the origin of the band-edge and yellow-band emissions from the pyramids, the wavelength-resolved cathodoluminescence properties of normal and cleaved pyramids were investigated in plan and/or cross-sectional configurations. The cross-sectional cathodoluminescence images of cleaved pyramid samples revealed significant differences between the overgrown areas on top of the mask and coherently grown regions over the windows. A precise reverse (or identical) contrast between the band-edge (or yellow-band) emission intensity and threading dislocation density was detected by comparing cross-sectional cathodoluminescence and transmission electron microscopic images. It was demonstrated that a strong correlation existed between structural defects and optical properties in laterally overgrown hexagonal pyramids.

Spatially Resolved Cathodoluminescence of Laterally Overgrown GaN Pyramids on (111) Silicon Substrate - Strong Correlation between Structural and Optical Properties. Y.H.Cho, H.M.Kim, T.W.Kang, J.J.Song, W.Yang: Applied Physics Letters, 2002, 80[7], 1141-3