Epitaxial relationships between GaN and Al2O3(0001) substrates
GaN thin layers (200 Angstrom) were grown by gas-source molecular beam epitaxy on c-plane Al2O3 substrates, Transmission electron microscopy reveals that two different epitaxial relationships may occur, The well-known GaN orientation with the c axis perpendicular to the Al2O3 surface and <1(1)over bar 00>parallel to<11(2)over bar 0> is observed when the substrate is nitridated prior to the growth. On the other hand, GaN layers deposited on bare Al2O3 surfaces exhibit a different crystallographic orientation: <11(2)over bar 0>parallel to<1(1)over bar 00> and <1(1)over bar 03>parallel to<11(2)over bar 0>. This corresponds to a tilt of about 19 degrees of the c axis with respect to the substrate surface. (C) 1997 American Institute of Physics.
1997
70
5
643
645
REVIEWED