Dislocation density and tetragonal distortion of a GaN epilayer on Si (1 1 1): A comparative RBS/C and TEM study

Rutherford backscattering and channeling spectrometry (RBS/C) as well as transmission electron microscopy (TEM) are used to characterize the crystalline structure of a GaN layer grown on a Si (1 1 1) substrate. The channeling measurements are performed along the off-normal 〈12^¯13〉 axis in the {101^¯0} plane of the GaN layer. The threading edge dislocation defect density obtained from RBS/C is quantitatively compared to the results obtained from TEM. The strain is found not to be completely relaxed, e_T ≠ 0, in spite of the large thickness of the GaN layer (3.0 μm), and in spite of the incorporation of various buffer layers