Published in J. Vac. Sci. Technol. B 21 1812 (2003).
Plasma-assisted molecular beam epitaxy of GaN on porous SiC substrates
with varying porosity
Ashutosh Sagar (a), C. D. Lee (a), R. M. Feenstra (a), C. K. Inoki (b) and T. S. Kuan (b)
(b) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(b) Department of Physics, University at Albany, SUNY, Albany, NY 12222
Abstract
We have grown GaN on porous SiC substrates and studied the
effect of substrate porosity on the overgrown film quality in terms of
defect structure and density and film strain. The growth was performed
by plasma-assisted molecular beam epitaxy (PAMBE). The GaN films were
characterized by x-ray, transmission electron microscopy (TEM) and
wafer curvature measurements by surface profilometry. TEM images show
that the GaN film grown on porous substrates contains open tubes and a
low dislocation density in regions between tubes. We discuss various
growth mechanisms that can lead to these defect features in the GaN
film. However, we do not find any overall improvement in the x-ray
rocking curve FWHM of the GaN films grown on porous substrates
compared to those on nonporous substrates. It was found that the GaN
films grown on porous SiC were significantly more strain relaxed
compared to those grown on nonporous substrate. We propose various
mechanisms that can lead to the reduction in strain in GaN films grown
on porous substrates and compare the data with finite element analysis
(FEA) simulations of such a system.
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