Molecular beam epitaxy and characterization of Al0.6Ga0.4N epilayers

Abstract

We have performed a detailed investigation of the molecular beam epitaxy of AlGaN epilayers on AlN template on sapphire substrate. The effects of various growth parameters, including nitrogen flow rate, and Al and Ga fluxes on tuning the Al composition of these epilayers are studied. An atomically smooth surface with a root mean square roughness of ∼0.4 nm was measured for ∼0.5-μm thick Al0.6Ga0.4N when grown under slightly metal-rich conditions. It was observed that dislocation propagation originating from the substrate layers can effectively be reduced or terminated in AlGaN epilayers with the incorporation of sub-nm interfaces. A refractive index contrast of 0.09 with the underlying AlN template was measured at a wavelength of 400 nm, making it suitable for waveguiding applications.