Mapping misorientation and crystallographic tilt in GaN layers via polychromatic microdiffraction
The spatial distribution of strain, dislocations, and crystallographic orientation in uncoalesced and coalesced GaN layers grown on striped Si or SiC substrates was studied by polychromatic X-ray microdiffraction and high resolution monochromatic X-ray diffraction. Tilt boundaries formed at the column/wing interface depending on the growth conditions and geometry of the striped substrate. The measurements revealed that the free-hanging wings are tilted upward at room temperature. A misorientation between the GaN(0001) and the Si(111) or SiC(0001) surface normal is observed. Distinct structural properties of the pendeo and cantilever epitaxially grown samples are discussed.