Abstract
The lattice orientation of epitaxial GaN films grown on
r-plane sapphire substrates by atmospheric metalorganic vapor-phase epitaxy was investigated. It is generally known that nonpolar
a-plane GaN layers are grown on
r-plane sapphire substrates. However, high-resolution X-ray diffraction revealed the large misorientation of GaN grown on
r-plane sapphire when the growth temperature was increased from1100
°C to 1150
°C. The
c-axis was oriented to 25° from the surface normal toward the (1¯
1
0
1)
Sapphire orientation. In addition, the GaN grown at 1150
°C indicated crystal twinning. These results were attributed to the anisotropic strain that was enhanced by higher growth temperature.