An X-ray diffraction technique for analyzing structural defects including microstrain in nitride materials

X‐ray diffraction analysis of structural defects in a‐plane GaN grown on r‐plane sapphire by MOCVD

“…(1) (the solid line on the meshed plane is a guide for the eye only). Projection on the plane of FWHM vs. inclination angle is the same as the traditional plot [13,14,17]. For lattice planes with h -k = 3N±1, the excess broadening (B 2θ ) shown in Fig.…”

“…In comparison to m-GaN film grown on m-plane sapphire [17], a-GaN films showed most significant ω-scan broadening resulted from a small lateral coherence length. The value of c L // is also much less than the lateral coherence length found in c-GaN layers [12,14] For our a-GaN layers, the small c L // value can be qualitatively correlated with the high density of BSFs along the [0001] direction, as suggested by McLaurin [22]. However, using only two symmetric diffraction planes to extrapolate the lateral coherence length based on Williamson-Hall plot may overestimate lateral coherence length and therefore underestimate stacking faults density since Eq.…”

“…In order to assess the impact of these defects on device performance, and to reduce defect densities by improving the growth processes, a rapid turnaround method for routine defect characterization is required. In the past, investigations related to structural defects in non-polar GaN were typically carried out by transmission electron microscopy (TEM) [3][4][5][6], by observing optically active emissions using photoluminescence (PL) [3,6,7], using spatially resolved cathordoluminescence (CL) [8,9], and/or through structural analysis using X-ray diffraction (XRD) measurments [10][11][12][13][14]. Since luminescence measurements do not allow quantitative correlation, defect densities are often measured using TEM, which is destructive and requires lengthy sample preparation procedures.…”

“…A review of XRD techniques for analyzing III-nitrides can be found in the reference by Moram and Vickers [10]. For conventional c-plane GaN films, an XRD rocking curve approach has been routinely used to estimate structural defects in mosaic films [13,14], With this approach, which separates broadening terms based on their geometric dependence, it has been found to yield estimates of threading dislocation density that correlate very well with TEM results [15,16]. A further extension of the XRD rocking curve approach was proposed for analyzing basal-plane stacking faults (BSFs) and was experimentally demonstrated with m-plane GaN films [17].…”

“…3 Results and discussion For a mosaic film, a typical rocking curve (ω-scan) peak has a profile composed of several broadening contributions that can be characterized in terms of in-plane twist ( || Γ ), out-of-plane tilt ( ⊥ Γ ), lateral coherence length (L), and micro-strain (ξ) as described by [13,14]:…”