Epitaxial growth and characterization of high-quality aluminum films on sapphire substrates by molecular beam epitaxy

Abstract

High-quality Al epitaxial films with homogeneous thickness have been epitaxially grown on 2 inch sapphire substrates by molecular beam epitaxy with an in-plane alignment of Al[10]/Al₂O₃[100]. The as-grown about 200 nm-thick Al (111) films grown at 750 °C show excellent uniform thickness distribution over the whole 2 inch substrate and a very flat Al surface with the surface root-mean-square roughness of 0.6 nm, as well as high crystalline qualities with the Al (111) full width at half maximum as small as 0.05°. There is no interfacial layer existing between as-grown Al epitaxial films and sapphire substrates. Instead, sharp and abrupt Al/Al₂O₃ hetero-interfaces are achieved. The effects of the growth temperature on the surface morphologies and the crystalline qualities of the as-grown Al epitaxial films have been studied in detail. This achievement of Al epitaxial films is of great importance in the application of Al-based microelectronic devices.