Self-generated microcracks in an ultra-thin AlN/GaN superlattice interlayer and their influences on the GaN epilayer grown on Si(110) substrates by metal-organic chemical vapor deposition

We investigated the effect of an ultra-thin AlN/GaN superlattice interlayer (SL IL) on the GaN epilayer grown on Si(110) substrates by metal-organic chemical vapor deposition (MOCVD). It is found that microcracks (MCs) are self-generated in the SL IL region, which depend on the thickness of the SL IL. The MCs influence the characteristics of the GaN epilayers grown on the SL IL, such as surface morphologies, strain and structural qualities. Furthermore, different MC configurations depending on the SL IL thickness are observed, which imply the controllability of MC generation. Understanding of the mechanism and the optimization of the SL IL structure make it possible to grow crack-free high-quality GaN films on Si substrates for optical and electronic device applications.