GaN/AlN super-lattice structures on vicinal sapphire (0001) substrates grown by rf-MBE

GaN/AlN super-lattice structures (SLs) grown on the vicinal sapphire (0001) substrates by rf-MBE are investigated using various characterization techniques. The satellite XRD diffraction peaks originating from the SLs are clearly observed, which indicate an abrupt interface and good periodicity of the SLs. Cross-sectional TEM observations show differnet features of SLs grown on the various vicinal substrates, depending on whether macro-steps form on the surface or not. DUV-Raman measurements show unique spectra from the SLs, which are different from the usual GaN and AlN films. The usage of a proper vicinal substrate angle shows a great merit to obtain high quality GaN/AlN SLs.