Nucleation layer design for growth of a high-quality AlN epitaxial film on a Si(111) substrate

Abstract

A high-quality AlN epitaxial film has been grown on a Si(111) substrate by metal–organic chemical vapor deposition through designing the AlN nucleation layer. The structure of a low temperature nucleation layer hinders the formation of amorphous SiN_x in the AlN/Si heterointerface, reduces the dislocation density, and thereby improves the crystalline quality of the AlN epitaxial film. The influence of nucleation layer temperature on the surface morphology and the crystalline quality of the AlN epitaxial film is also revealed in detail. The AlN epitaxial film with the optimized nucleation layer grown at a temperature of 800 °C shows a sharp AlN/Si heterointerface, with an XRD full-width at half-maximum for AlN(0002) of 0.30°, and a very smooth surface with a root-mean-square surface roughness of 1.9 nm. Meanwhile, the 200 nm-thick AlN epitaxial film is almost fully relaxed with an in-plane tensile strain of only 0.42%. This work provides an effective approach for the growth of high-quality AlN epitaxial films in the application of AlN-based ultraviolet photonic devices and GaN-based optoelectronic devices.