Investigation of the properties and formation process of a peculiar V-pit in HVPE-grown GaN film

•The SEM and CL images of a hexagonal V-pit are obviously different.•No defects or dislocations contribute to the formation of such a V-pit.•A kinetically limited growth process of GaN is demonstrated. Hexagonal V-pits with an inverted pyramid shape appear on the surface of a GaN film after etching by hot H3PO4. A regular structure that is different from the V-pit morphology is observed in the cathodoluminescence image. The carrier concentration and stress distributions are nonuniform inside the V-pit. Furthermore, no dominant dislocations or defects are observed in the facets or bottom area of the V-pits. An island coalescence process is considered to contribute to the formation of such V-pits, with the coalesced island facets changing from {101m} to {112m} at a concave state for the different growth velocities.