Determination of tilt in the lateral epitaxial overgrowth of GaN using X-ray diffraction

Tilt that occurs during the lateral overgrowth of GaN over an SiO2 mask fro m (1 (1) over bar 0 0)(GaN)-oriented stripe openings is systematically meas ured using X-ray diffraction. This tilt is measured for a range of 'fill fa ctors' (ratio of stripe opening width to stripe period) and for changes in growth temperature and input V/III ratio. It is found that changes in these parameters have a significant effect on the extent and distribution of til t in the overgrown regions relative to GaN directly above the underlying 's eed' layer. Correlations between tilts and stripe morphologies as observed in scanning electron microscopy are made, and an explanation based on the ' local' V/III ratio around the growing stripes is proposed to account for th ese results. The aspect ratio of the stripes in cross section (which is aff ected by fill factor and growth conditions) is found to be directly related to the degree of wing tilt, suggesting that tilt may be affected by GaN wi ng/SiO2 interfacial forces. (C) 2000 Elsevier Science B.V. All rights reser ved.