Published in J. Electronic Materials 30, 162 (2001).
Properties of GaN epitaxial layers grown on 6H-SiC(0001) by
plasma-assisted molecular beam epitaxy
C. D. Lee (a), V. Ramachandran (a), Ashutosh Sagar (a),
R. M. Feenstra (a), D. W. Greve (b), W. L. Sarney (c), L. Salamanca-Riba (c),
D. C. Look (d), Song Bai (e), W. J. Choyke (e), and R. P. Devaty (e)
(a) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b) Department Electrical and Computer Engineering, Carnegie Mellon University,
Pittsburgh, PA 15213
(c) Materials and Nuclear Engineering Department, University of
Maryland, College Park, MD 20742-2115
(d) Wright State University and Air Force Research Laboratory,
Dayton, Ohio 45435
(e) Department of Physics and Astronomy, University of Pittsburgh,
Pittsburgh, Pennsylvania 15260
The structural, electrical, and optical properties of GaN grown on
6H-SiC(0001) substrates by molecular beam epitaxy are studied.
Suitable substrate preparation and growth conditions are found to
greatly improve the structural quality of the films. Threading
dislocation densities of about 1x109 cm-2 for edge
dislocations and less than 1x106 cm-2 for screw
are achieved in GaN films of 0.8 micrometer thickness. Mechanisms of
dislocation generation and annihilation are discussed. Increasing the
Ga to N flux ratio used during growth is found to improve the surface
morphology. An unintentional electron concentration in the films of
about 5x1017 cm-3 is observed, and is attributed to
excess Si in the films due to a Si-cleaning step used in the substrate
preparation. Results from optical characterization are correlated
with the structural and electronic studies.
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