Evolution of Dislocations and Strains in AlN Grown by High-Temperature Metal-Organic Chemical Vapor Deposition

High-quality aluminum nitride (AlN) templates are essential for the development of optoelectronic and electronic devices. Here, the evolution of strains and dislocations during AlN epitaxy on commercially available sputtered AlN/sapphire substrates was comprehensively investigated. The presence of small and uniform grains in the sputtered AlN nucleation layer (NL) results in smaller strain levels and fewer dislocations at the interface during metal-organic chemical vapor deposition (MOCVD) of a high-temperature AlN thin film. Dislocations are annihilated in the form of dislocation loops or undergo 90 degrees bending, contributing to better crystalline quality compared to AlN grown on NL prepared by MOCVD. However, a higher strain level was identified in AlN grown on sputtered NLs, where the strain was released through thin film cracking. Modulation of different stages during AlN growth is necessary toward a balance between thin film quality and strain relaxation.