Heteroepitaxy between wurtzite and corundum materials

Abstract

Heteroepitaxy of wurtzite semiconductors on corundum substrates is widely used in modern optoelectronic devices, because both crystals belong to the same hexagonal close-packed system. However, the constituent atoms in the wurtzite structure align in an ideal hexagon within the (0001) plane, whereas those in the corundum structure are displaced due to empty octahedral sites. Herein, we demonstrate that this atomic arrangement mismatch at the interface generates low-angle grain boundaries in epilayers, and step bunching of corundum substrates with an even number of molecular layers can eliminate the boundaries. Furthermore, we propose that the weakened epitaxial relationship between epilayers and substrates also eliminates low-angle grain boundaries, which may be useful for practical applications.