-LiAlO2E. S. Hellman
Bell Laboratories, Lucent Technologies
Z. Liliental-Weber
Materials Science Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720
D. N. E. Buchanan
Bell Laboratories, Lucent Technologies
-LiAlO2 has
attracted attention as a possible substrate for GaN epitaxial growth. This is
partly because this face has an excellent lattice and structural match to
(1 
0 0) GaN. This orientation would have a misfit of
only -1.4% along the c-direction and -0.1% along the b-direction
of LiAlO2. We find that in practice this orientation relationship
does not occur; instead, (0 0 0 1) oriented GaN grows with a
small tilt (0.6° towards the c-direction) between the film and
substrate. Although the misfit along the substrate b direction is large
(-6.3%) for this orientation, the tilt perfectly accommodates the -1.4% misfit
in the c direction. We present characterization of these films by RHEED,
X-ray diffraction, and TEM. We propose that the tilt is driven by a reduction
of interface energy which occurs in polar, incoherent interfaces.
© 1997-1998 The Materials Research Society
