Growth of High Quality GaN by Hydride Vapor Phase Epitaxy

Hydride vapor phase epitaxy (HVPE) is currently used as a practical method for preparing GaN substrates. However, the reduction of dislocation density and the minimization of wafer curvature are dispensable from device application point of view. To reduce the dislocation density, the authors proposed facet -initiated epitaxial lateral overgrowth (FIELO) method. This method makes it possible to bend and reduce threading dislocations in GaN by forming GaN facet structures near the initial growth stage on foreign substrate, such as sapphire. In addition to the use of stripe-type mask pattern in the FIELO method, a novel FIELO method starting from random-islands having facet sidewalls of GaN formed at relatively low temperature is studied. It is shown that this method is superior to the conventional FIELO for reducing both of dislocations at the hetero-interface and the curvature of freestanding GaN crystal.