GaN was grown on bulk GaN(000-1) surfaces by MBE using ammonia. These very smooth substrates allow the morphologies seen in two growth regimes to be distinguished. Under excess Ga, atomically smooth hexagonal posts with micron dimensions are observed. With excess ammonia there are macrosteps between hillocks. Filled zones and partially denuded zones have been observed on terraces between the macrosteps. The filled zones are only observed on quenched samples. The ratio of denuded to filled zones depends on the cooling procedure after growth. The denuded zones appear to always originate from the lower step edge of a (macro)step.