| By varying metalorganic chemical vapor deposition (MOCVD) growth conditions, III-nitride samples with dislocation densities ranging over two orders of magnitude were grown, and the effects of dislocations were studied. Initially, a novel technique to determine dislocation density by high-resolution x-ray diffraction (HRXRD) was developed. Results were compared to those obtained by transmission electron microscopy (TEM) and agreed within a factor of 1.5. This HRXRD-based technique provided rapid and accurate feedback for use in growth-optimization studies; and became a basis for future studies of the effects of dislocation on specific phenomena associated with III-nitride technology. This included a study of the effect of dislocations on impurity incorporation during MOCVD growth. Dislocations were previously conjectured to provide energetically favorable sites for impurity incorporation, but experimental results did not confirm this.; Finally, a novel growth technique was investigated for gallium nitride (GaN) bulk crystals, based on a simple dissolution/recrystallization process. GaN was successfully dissolved in a molten LiCl medium, and then recrystallized on a nominally homoepitaxial MOCVD-grown GaN template. This provides the basis for a potentially viable method to fabricate high quality GaN bulk crystals for homoepitaxial growth. |
