Growth behavior of ammonothermal GaN crystals grown on non-polar and semi-polar HVPE GaN seeds

In this work, GaN crystals were grown on non-polar and semi-polar HVPE GaN seeds by the basic ammonothermal method. The growth behaviors of various crystal planes were investigated. Different surface morphology regimes were observed with features including hillock-, slate- and elliptical sphere-like surfaces. The growth rates and evolution processes of various planes of the as-grown GaN crystals were characterized using scanning electron microscopy (SEM) and cathodoluminescence (CL) measurements. Our results suggest that the growth rates of identical crystal planes grown on HVPE seeds with different orientations are almost the same. The dominant facets of these GaN crystals were ultimately found to be non-polar m-planes, {10-11} semi-polar planes and polar (000-1) planes by analyzing the morphological evolution of the crystal shape using the kinetic Wulff's rule.