A study of GaN regrowth on the micro-faceted GaN template formed by in situ HCl etching

This study demonstrates improvement of crystal quality of GaN film by growing it on a micro-faceted GaN template fabricated by in situ etching with an HCl/N2 etching gas mixture at 1050 °C in hydride vapor phase epitaxy (HVPE) reactor. Cathodoluminescence images of the cross-sectional structure showed that there were six sublays in the GaN film grown with in situ etching for five times. Etch pit density (EPD) and high-resolution X-ray diffraction (HR-XRD) measurements showed that the crystal quality of GaN thick film grown on micro-faceted GaN template was better than that of the as-grown GaN. A large number of columnar structures were formed on the micro-faceted GaN template at the initial stage of regrowth process, the coalescence of which played an important role in the reduction of threading dislocation density during the GaN growth. A model has been developed to explain the mechanism of forming process of the columnar structures.