An X-ray diffraction technique for analyzing basal-plane stacking faults was introduced and tested on GaN. The analysis considered the coexistence of multiple X-ray broadening terms including tilt, twist, limited coherence length and inhomogeneous strain. By measuring and fitting a series of symmetrical and asymmetrical reflection planes, the lattice tilt, twist, lateral coherence length and inhomogeneous strain contributions were deduced; which permitted the determination of the existence of any additional broadening in m-plane GaN. It was found that, in fact, certain ω-scans did exhibit excess broadening and that their lattice-plane dependence was similar to the functional dependence of basal-plane stacking faults derived for powder X-ray diffraction (θ/2θ-scan). Applying such a functional dependence permitted the estimation of the basal-plane stacking fault densities (I1- and I2-type). The typical stacking fault density was estimated to be 106/cm in m-plane GaN grown on m-plane sapphire by MOCVD, while the relative densities of I1- and I2-type were sample-dependent. In contrast to the m-plane GaN, stacking faults in GaN on c-plane sapphire did not contribute significantly to Bragg peak broadening and were below the detection limit.

An X-Ray Diffraction Technique for Analyzing Basal-Plane Stacking Faults in GaN. Q.S.Paduano, D.W.Weyburne, A.J.Drehman: Physica Status Solidi A, 2010, 207[11], 2446–55