CBED study of grain misorientations in AlGaN epilayers.
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.
Sahonta
S-L
SL
H.H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, UK. suman-lata.sahonta@bristol.ac.uk
Cherns
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D
Liu
R
R
Ponce
F A
FA
Amano
H
H
Akasaki
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I