UC Santa Barbara

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.