Measurements of strain in GaN films grown via pendeo-epitaxy indicated that the overgrowth, or wing, material was crystallographically relaxed. An increase of about 0.02% in the c-axis lattice parameter of the wing material was measured via high-resolution X-ray diffraction; additional evidence for this increase was indicated by an upward shift of the E2 Raman line frequency. Atomic force microscopy studies revealed a reduction in the density of mixed-type dislocations in the wing. A reduction in screw-type dislocations in the wings with respect to the stripes was indicated by a reduction in high-resolution X-ray diffraction rocking curve FWHM of the (00•2) reflections from 646 to 354arcsec. The off-axis FWHM of the wing area was 126arcsec compared to 296arcsec for the stripe indicating a reduction in the edge-type dislocations as well. Pendeo-epitaxy growth of wings off the (11•0) surface of a GaN stripe produced a material that was crystallographically relaxed, contains fewer defects compared to the stripe and was atomically smooth on the (11•0) surface.

Strain and Dislocation Reduction in Maskless Pendeo-Epitaxy GaN Thin Films. A.M.Roskowski, P.Q.Miraglia, E.A.Preble, S.Einfeldt, T.Stiles, R.F.Davis, J.Schuck, R.Grober, U.Schwarz: Physica Status Solidi A, 2001, 188[2], 729-32