Published in J. Electron. Mater. 32, 855 (2003).
Growth of GaN on porous SiC and GaN substrates
C. K. Inoki (a), T. S. Kuan (a), C. D. Lee (b), Ashutosh
Sagar (b), R. M. Feenstra (b), D. D. Koleske (c), D. J. Diaz (d), P. W.
Bohn (d), and I. Adesida (d)
(a) Department of Physics, University at Albany, SUNY, Albany, NY 12222
(b) Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213
(c) Chemical Processing Science Dept., Sandia National Laboratories, Albuquerque, NM 87185
(d) Beckman Institute, University of Illinois, Urbana, IL 61801
Abstract
We have studied the growth of GaN on porous SiC and GaN substrates, employing
both plasma-assisted molecular beam epitaxy (PAMBE) and metalorganic chemical
vapor deposition (MOCVD). For growth on porous SiC, transmission electron
microscopy (TEM) observations indicate that the epitaxial GaN growth initiates
primarily from surface areas between pores, and the exposed surface pores
tend to extend into GaN as open tubes and trap Ga droplets. The dislocation
density in the GaN layers is similar to, or slightly less than, that observed
in layers grown on non-porous substrates. For the case of GaN growth on
porous GaN the overgrown layer replicates the underlying dislocation structure
(although considerable dislocation reduction can occur as this overgrowth
proceeds, independent of the presence of the porous layer). The GaN layers
grown on a porous SiC substrate were found to be mechanically more relaxed
than those grown on non-porous substrates; electron diffraction patterns
indicate that the former are free of misfit strain or are even in tension
after cooling to room temperature. Significant changes in the stress of
the overgrown layers on porous GaN were also found, as seen in line shifts
of low-temperature photoluminescence spectra.
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