MBE of AlN on SiC and influence of structural substrate defects on epitaxial growth

Aluminum nitride layers were grown on Si-terminated SiC (0 0 0 1) at various substrate temperatures, growth rates, and V/III-ratios in a RF-plasma enhanced MBE system. Surface morphology detected by AFM is strongly influenced by V/III-ratio. Smooth surfaces with a RMS-roughness below 1 nm are obtained for stoichiometric growth conditions giving the smallest FWHM of the XRD-rocking curves of 190 arcsec. For the growth of a more rough AlN-surface layer (RMS 2–24 nm) atomically smooth areas have been detected around micropipes by AFM indicating changed growth conditions. Lateral extension of this area is increased by reducing the growth rate or the V/III-ratio.