  GaN films with thickness up to 3 mm were grown by halide vapour phase epitaxy
method. Two growth modes were observed: the high temperature (HT) mode and the
low temperature (LT) mode. Films grown in HT mode had smooth surface, however
the growth stress was high and caused cracking. Films grown in LT mode had
rough surface with high density of V-defects (pits), however such films were
crack-free. The influence of growth parameters on the pit shape and evolution
was investigated. Origins of pits formation and process of pit overgrowth are
discussed. Crack-free films with smooth surface and reduced density of pits
were grown using combination of the LT and HT growth modes.
