Ultra-flat and high-quality AlN thin films on sapphire (0001) substrates grown by rf-MBE

摘要

AlN films on sapphire (0001) substrates grown by plasma-assisted molecular beam epitaxy are investigated. In-situ reflection high-energy electron diffraction shows a streak pattern from the beginning of the AlN growth indicating the 2-dimensional (2D) growth mode of AlN. High-resolution X-ray diffraction measurements illustrate that the full-width at half maximum of AlN (0002) peak is less than 80 arcsec when the thickness of AlN is more than 200 nm showing high structural film quality. Clear near-band edge emission at 77 K is observed from an 800 nm-thick AlN film by cathodoluminescence measurements. Atomic force microscopy observations show ultra-flat surface morphologies of AlN with rms as small as 0.12 nm. All characterization results suggest the high-quality of AlN films.