Epitaxial growth of bulk semipolar aln films on Si(001) and hybrid SiC/Si(001) substrates

The possibility of growing bulk (more than 7 $\mu$m thick) epitaxial semipolar AlN films on Si(001) and hybrid SiC/Si(001) substrates without cracks has been investigated. It is found that an AlN layer grown on the Si substrate is extended, whereas an AlN layer grown on the hybrid SiC/Si substrate is compressed. The limiting (critical) thickness of the semipolar AlN layer on the Si(001) substrate is determined to be $\sim$ 7.5 $\mu$m. When the film thickness exceeds this value, an ensemble of cracks is formed in the film, leading to its total cracking and exfoliation from the substrate. The semipolar epitaxial AlN films with a thickness of more than 40 $\mu$m are grown on hybrid SiC/Si substrates without cracking and exfoliation from the substrate.