On the dependence of internal stress on dislocation inclination pattern in HVPE-GaN substrates

Internal stress in gallium nitride (GaN) induced during epitaxy growth can degrade the performance of GaN devices. This work studied the internal stress distribution and dislocation configuration around an inclusion of ∼300 μm in GaN substrates grown by hydride vapor phase epitaxy, by means of combined Raman spectroscopy, x-ray topography, and two-photon excitation photoluminescence. The inclusion-induced internal stress decreased exponentially along the radial direction. However, the internal stress, though reduced to a small magnitude, was unexpectedly maintained and propagated over long distances. A stress localization phenomenon, which was out of the prediction of classic elasticity theory, was also observed. The inclination of threading dislocations was found to be substantially influenced by the unreported distribution of internal stress. Four characteristic dislocation inclination patterns were identified: the two-short-tooth pattern, two-long-tooth pattern, gear pattern, and sun-like pattern. The dependence of internal stress on the dislocation inclination pattern was revealed. Based on this dependence, a method to predict the stress field in crystal based on dislocation pattern without corrosion was proposed.