The polarity of AlN films grown on Si(111)

The nucleation and subsequent growth of high-quality AlN layers of both cry stallographic polarities on nonpolar Si(1 1 1) substrates were investigated . The films were grown by plasma-assisted molecular beam epitaxy. The nucle ation conditions of the epitaxial AIN on Si(1 1 1) surface were found to be critical for the formation of the AIN films either with Al- or N-face. The existence of a 7 x 7-reconstructed Si(1 1 1) surface is also found to be i mportant to provide a proper nucleation and subsequent two-dimensional grow th of the AlN (0 0 (0) over bar 1) and (0 0 0 1) oriented films. The AlN fi lm polarity determination has been performed either ex situ by X-ray photoe lectron diffraction or in situ by observing the polarity-dependent surface reconstructions. Finally, the AIN layers of both polarities were characteri zed by atomic force microscopy to provide information about the surface mor phology of the grown films. (C) 1999 Elsevier Science B.V. All rights reser ved.