Growth of atomically smooth AlN films with a 5:4 coincidence interface on Si(111) by MBE

Epitaxial aluminum nitride AlN(0001) thin films have been grown by plasma-assisted molecular beam epitaxy (PA-MBE) on Si(111). The influence of the composition of the nitrogen plasma on the crystal quality, as judged by X-ray diffractometry (XRD) and atomic force microscopy (AFM). has been investigated. Under an Al/N vapor phase ratio close to unity atomically smooth AlN films have been grown at 850 degrees C substrate temperature with maximum growth rates of 2.5 nm min(-1). A root 3 x root 3 and a more Al-rich 2 x 6-surface reconstruction have been observed. Transmission electron microscopy (TEM) investigations show that these films are homogeneous 2H-AlN single crystals. Their defect structure consists of threading dislocations mostly. The hetero-interface is abrupt and flat. Processed high-resolution (HR) TEM images demonstrate a 4 x d(si((1) over bar 00)) to 5 x d(AlN((2) over bar 110)) coincidence between substrate and epilayer. The XRD FWHM of the (0002)-diffraction peak of 0.5 mu m AlN is 0.06 degrees in the omega/2 theta scan and 0.32 degrees in the omega scan. Phonon modes of AlN have been detected by Raman and infra-red spectroscopy. (C) 1998 Elsevier Science S.A. All rights reserved.