title: CBED study of grain misorientations in AlGaN epilayers.
abstract: Large angle convergent beam electron diffraction (LACBED) has been used to examine AlGaN epilayers grown by facet-controlled epitaxial lateral overgrowth on GaN/(0001) sapphire substrates in prototype UV laser structures. The substrates, defined by masks with seed openings along a <10-10> stripe direction, had GaN seed columns with {11-22} surfaces. Studies were carried out on cross-sectional samples cut perpendicular to the stripe axis. An LACBED analysis of the orientation of (000 2) planes, and of the (11-20) planes parallel to the stripe axis, revealed that the AlGaN wings were both rotated by angles of 1-2 x 10(-2)radians about the 10-10 stripe axis with respect to the underlying GaN, and distorted due to misfit strains. It is shown that the results are consistent with the observed structure of the AlGaN/GaN and the wing/wing boundaries, and with a new model for the generation of a-type misfit dislocations at the AlGaN/GaN interface.
authors.affiliation: H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK. suman-lata.sahonta@bristol.ac.uk
authors.forename: S-L
authors.initials: SL
authors.lastname: Sahonta
authors.forename: D
authors.initials: D
authors.lastname: Cherns
authors.forename: R
authors.initials: R
authors.lastname: Liu
authors.forename: F A
authors.initials: FA
authors.lastname: Ponce
authors.forename: H
authors.initials: H
authors.lastname: Amano
authors.forename: I
authors.initials: I
authors.lastname: Akasaki