Surface morphology study of basic ammonothermal GaN grown on non-polar GaN seed crystals of varying surface orientations from m-plane to a-plane

GaN crystals were grown on hydride vapor phase epitaxy (HVPE) GaN seed crystals with non-polar surface orientations varying between on-axis m-plane and a-plane using the basic ammonothermal method. Three different surface morphology regimes were observed with the surface features including mounds, slate-like morphologies, and pyramidal ‘spikes’ composed of (0001) and non-polar microfacets. A macroscopic off-orientation of the non-steady-state surface and newly appearing steady-state growth surfaces towards [0001¯] by approximately 1° was observed with geometric constraints suggesting an off-orientation of the observed {10–10} microfacets towards [0001¯] by approximately 1° or greater.

► Ammonothermal growth was performed on GaN crystals of varying nonpolar orientation. ► Surface morphology was examined and three different regimes were observed. ► Observed features included mounds, slate-like morphologies, and pyramidal ‘spikes’. ► A macroscopic off-orientation of m-plane facets by 1° towards [000–1] was observed.