Molecular beam epitaxial growth of AlN single crystalline films on Si (111) using radio-frequency plasma assisted nitrogen radical source

Abstract

We have grown AlN films on Si (111) using a molecular beam epitaxy (MBE) approach in which reactive nitrogen species are generated in a remote 13.56 MHz radio-frequency plasma discharge, nitrogen radical source. Effects of the Al/Si (111) γ-phase on epitaxial growth of AlN on Si (111) has been studied. Successive processes of forming stable Al/Si (111) γ-phase at 800 °C followed by MBE growth without interrupting Al beam exposure was effective to prevent amorphous SiNx formation on Si substrate. The Al/Si (111) γ-phase was found effective to fix the orientation relationship between AlN and Si for epitaxial growth of single crystal AlN. Single crystal AlN was grown on the Al/Si (111) γ-phase at the temperature as low as 400 °C. By optimizing growth conditions (substrate temperature, V/III ratio and plasma conditions), growth of single crystal AlN films in a quasi-layer-by-layer fashion was observed for the thickness up to 60 nm. The optimized value on the growth temperature was 800 °C and that on the V/III ratio was 440. The surface of the AlN film grown under the optimized condition was quite smooth with a root mean square roughness of 0.3 nm. The resistivity of the film was about 2×109 Ω cm.