Strain and dislocation reduction in maskless pendeo-epitaxy GaN thin films
Roskowski, A. M., Miraglia, P. Q., Preble, E. A., Einfeldt, S., Stiles, T., Davis, R. F., ... Schwarz, U. (2001). Strain and dislocation reduction in maskless pendeo-epitaxy GaN thin films. Physica Status Solidi (A) Applied Research, 188(2), 729-732.
Measurement of strain in GaN films grown via pendeo-epitaxy (PE) indicates that the overgrowth, or wing, material is crystallographically relaxed. An increase of approximate to0.02% in the c-axis lattice parameter of the wing material was measured via high-resolution X-ray diffraction (HRXRD); 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 is indicated by a reduction in HRXRD rocking curve FWHM of the (0002) reflections from 646 to 354 arcsec. The off-axis FWHM of the wing area was 126 arcsec compared to 296 arcsec for the stripe indicating a reduction in the edge-type dislocations as well. Pendeo-epitaxy growth of wings off the (1120) surface of a GaN stripe produced a material that is crystallographically relaxed, contains fewer defects compared to the stripe and is atomically smooth on the (1120) surface.