Growth of atomically smooth AlN layers on Si(111) substrates through an amorphous Si$_x$N$_y$ layer by plasma-assisted molecular beam epitaxy

The study focuses on the growth of AlN layers on Si(111) substrates using plasma-assisted molecular beam epitaxy. The influence of the substrate temperature on the crystalline quality of the AlN layers is systematically investigated. It is demonstrated that the predeposition of an amorphous Si$_x$N$_y$ layer on the Si(111) surface followed by the deposition of approximately 2 monolayers of Al allows one the formation of AlN layer with a surface roughness as less as 0.43 nm at a layer thickness of 170 nm. The results are of interest for the monolithic integration of III–N optoelectronic and radio frequency devices with silicon-based technologies.