TRANSMISSION ELECTRON-MICROSCOPY OF DEFECTS IN GAN FILMS FORMED BY EPITAXIAL LATERAL OVERGROWTH

We have investigated by transmission electron microscopy (TEM) defect morphology and structure in GaN films formed using an epitaxial latera l overgrowth (ELO) technique on SiO2-mask/window-stripe-patterned GaN layers in hydride vapor-phase epitaxy. In this experiment, the regions overgrown on the SiO2 masks were thoroughly examined. Cross-sectional TEM clearly revealed characteristic defects along the [0001] directio n in the overgrown region, which consisted of arrays of dislocations r unning along the mask stripe direction. These defects caused crystallo graphic tilting in that region near the mask with respect to the other region grown from the window area. We also observed, at the coalesced site on the mask, vertical repropagation of dislocations that had pro pagated laterally during ELO. The origin of the observed defects and t heir influence on the residual dislocation distribution near the fi:im surface are discussed. (C) 1998 American Institute of Physics.