Published in J. of Vac. Sci. Technol. A 17, 1289 (1999).
Temperature dependence of molecular beam epitaxy of GaN on SiC (0001)
V. Ramachandrana, A. R. Smitha, R. M. Feenstraa and
D. W. Greveb
aDepartment of Physics, b Department of Electrical and
Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213
High quality gallium nitride (GaN) thin films have been grown on
6H-silicon carbide (0001) substrates at varying substrate temperatures
using molecular beam epitaxy and characterized at low and high film
thicknesses. The epitaxial layers show two regimes in temperature
distinguishable by different morphology. For film thicknesses around
the critical thickness, low temperature growth is two dimensional
while for higher temperatures, growth is in the form of 3-D columnar
islands. At a thickness of about 200 nm, the low temperature films
show a large density of spiral growths while high temperature films
show a 2-dimensional morphology. X-ray peak widths are seen to
decrease with increasing substrate temperature. These results have
been explained in terms of a model which proposes different misfit
dislocation formation mechanisms in the two temperature regimes.
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