Recent progress in basic ammonothermal GaN crystal growth

•Round shape of seeds allowed to crystallize GaN without cracks at the edges.•60 µm/day growth rate in ammonothermal crystallization is presented.•Etch pit density in laterally-grown GaN was of the order of 102 cm−2.•Stress Induced Polarization Effect (SIPE) was visible in Am-GaN crystals. Progress in basic ammonothermal gallium nitride crystallization is reported. In order to prevent the appearance of cracks in growing GaN a new shape of native seeds is proposed. Crystallization results on irregular (old) and round (new) shapes are compared in terms of growth rate and structural quality. The new type of seeds allowed to grow crystals twice as fast without losing the very high structural quality. Etch pit density in the new-grown material is examined and compared to that in the seeds. Material deposited in vertical and lateral directions is analyzed. In the latter case the etch pit density is as low as 102 cm−2. An influence of growth process parameters and crystal growth configuration on the structural quality of crystallized GaN is discussed.