An increase of threading dislocations filtering efficiency in AlN/$c$-Al$_{2}$O$_{3}$ templates with faceted surface morphology during a growth by molecular beam epitaxy

The results of transmission electron microscopy study and X-ray diffraction analysis of AlN/$c$-Al$_{2}$O$_{3}$ templates with GaN ultrathin insertions grown by plasma-assisted molecular beam epitaxy are presented. It is shown that AlN buffer layers with faceted surface morphology provide a much higher threading dislocations density reduction then with smooth layers. The filtering action of ultrathin GaN insertions is confirmed.