Analysis of HVPE grown AlGaN layers on honeycomb patterned sapphire

•HVPE grown AlGaN layers on patterned sapphire substrates were analyzed. XRD was used to determine three different orientations of AlGaN in the layers•EBSD was used to determine protruding crystallites which hinder c-plane layer coalescence.•All crystallites found with XRD texture analysis could be found and addressed with EBSD and cross-sectional SEM. Two orientations were addressed to be already published (11–22) and (1–103) AlGaN nucleating on m-plane sapphire sidewalls.•Protruding crystallites which hinder layer coalescence is proposed to be c-plane AlGaN on n-plane sapphire according to schematic.

Thick AlxGa1−xN layers were grown by hydride vapor phase epitaxy on hexagonally patterned sapphire substrates. Non-c-planar growth is found inside the etched honeycombs which in part hinders coalescence of the c-plane AlGaN layer growing on top of the ridges. From X-ray diffraction, electron backscatter diffraction and scanning electron microscopy, the orientations of the parasitic crystallites were identified as {11–22} and {1–103} AlGaN growing on m-plane sapphire sidewalls as well as c-plane oriented AlGaN growing on n-plane sidewall facets which are located in the corners of the combs. According to the geometry of parasitic crystallites, it is further observed, that the semipolar growth occurring on sapphire m-plane sidewalls does not hinder the coalescence of c-plane AlGaN growing on top of the ridges, whereas fast propagation of parasitic crystallites nucleating on n-plane sidewall facets leads to delayed layer coalescence.