Cross-section SEM images of the two CE GaN layers with the view along the GaN direction: (a) sample A and (b) sample B.
Scheme of the PXM geometry showing the sample with stripes running in the direction.
Series of Laue diffraction patterns taken by PXM for sample A for different probe positions across the stripe: (a) left GaN wing, (b) GaN column, (c) right GaN wing, and (d) gap between the wings. (e) Full Laue pattern corresponding to the position (a) where the region of interest used in (a)–(d) is marked by a dashed circle.
Series of Laue diffraction patters taken by PXM for sample B for different probe positions across the stripe: (a) right GaN wing, (b) gap between two GaN wings, and (c) left GaN wing.
HRXRD reciprocal space maps of the GaN(0002) reflection for sample A (a) and sample B (b), respectively. The diffraction plane was perpendicular to the GaN stripes.
Typical intensity profiles of the GaN(0006) Laue reflection from the left wing (green), the column (red), and the right wing (blue) along the direction for sample A (a) and sample B (b), and along the direction for sample A (c) and sample B (d). Typical (0006) GaN Laue spots in the column regions (e) and wing (f) regions of samples A and B [(g) and (h)].
Width of the GaN(0006) Laue reflection along the (a) and directions taken at 50% of the peak intensity for sample A (open triangles) and at 60% of the peak intensity for sample B (filled boxes).
Results of FE simulations for a thermal load of of sample A [(a) and (b)] and sample B [(c)–(f)], respectively. The normal strain along the direction [(a), (c), and (e)] and the displacement along the direction [(b), (d), and (f)] at different distances from the interface on top of the ridges are shown as line scans in the direction across the stripe. Two different sample geometries are considered for sample B. The GaN growing from the sidewalls of the Si ridges is assumed to be separated from the GaN wings above the interface by a small gap for (c) and (d). In contrary the GaN is continuous over the interface at for (e) and (f).
Schematic view of the cross-sectional plane of the CE grown GaN on Si which was divided into three regions (a). Schematic of the crystallographic tilt by in region I along the direction (b) and in region II along the direction (c). Dependence of the crystallgraphic tilt angle on the linear MD density for different values of the Si miscut angle given in degrees (d).
Side-view SEM images of samples A (a) and B (b). Inserts show OIM analysis results.
SEM image of the two neighboring cells in the wing region of the sample A chosen for OIM analysis are shown with dashed rectangle. OIM analysis of the two neighboring cells in the wing region of the sample A (middle). Pole figures of the two cells (bottom). Insert shows overlapped central parts of the two pole figures for two cells. Centers of the pole figures of the two cells are displaced parallel to the stripe direction demonstrating misorientation due to a small angle boundary separating two growth cells.
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