High Resolution X-Ray Diffraction and Rutherford Backscattering Spectroscopy Studies on Laser Molecular Beam Epitaxy Grown GaN Layers on Sapphire (0001)

GaN epitaxial layers have been grown hetero-epitaxially on c-plane sapphire substrate using laser molecular beam epitaxy under various growth processes. Different targets such as liquid gallium metal and bulk GaN polycrystalline targets were ablated for the GaN growth either in the presence of r.f. nitrogen plasma or under high pressure nitrogen ambient. The GaN layers grown under r.f. nitrogen plasma were found to grow epitaxially on sapphire (0001) substrates with good crystalline quality. The high resolution (0002) plane X-ray rocking curve measurements revealed the full width at half maximum of 110 and 245 arc sec while the Rutherford backscattering geometry offered a very low yield of 5.9 and 2.3% for the GaN layers grown using liquid gallium and bulk GaN targets under r.f. nitrogen plasma, respectively. Our results indicate that the GaN layers grown using bulk GaN poly target and r.f. nitrogen plasma have superior structural properties.