Formation of m-plane AlN on plasma-nitrided m-plane sapphire

Microwave plasma using a gas mixture of N2 and H2 has been applied for the nitridation of m-plane sapphire substrate to form a thick epitaxial AlN film. The X-ray diffraction results show that the AlN films formed on the sapphire surface by nitridation for a period from 10-60 min are in (10 1 ¯ 0) orientation and have an epitaxial relationship with the substrate. The thickness of the nitride film increases with nitridation time and approaches about 0.5 m after nitridation for 1 h, while the film surface becomes rough. The film quality is reasonably good, as evaluated with the X-ray rocking curve of (10 1 ¯ 0) AlN. Faceted voids in the sapphire substrate underneath the AlN are also observed with inclined a-plane facets after nitridation.