Structured wide bandgap semiconductor thin films have been developed as a technique for growing thin films with low threading dislocation densities. A growth technique called Pendeo-Epitaxy (PE) has been applied to the deposition of GaN and AlGaN thin films. Low densities of dislocations on GaN stripes on AlN/6H-SiC(0001) and AlN/3C-SiC(111)/Si(111) substrates have been achieved. The dislocation density was reduced by at least five orders of magnitude. The characterization of the resulting materials is being reported in this paper. By using a mask on the [11¯00]-direction oriented GaN stripes, the vertical propagation of threading dislocations during PE regrowth is blocked. Tilting in the laterally moving growth fronts, and associated crystallographic misregistry in the areas of coalescence over the stripes, and the generation of dislocations propagating from the resulting boundaries has been observed. A potential solution to this problem has been developed and is based on the elimination of the mask, as determined via X-ray diffraction and scanning and transmission electron microscopies.