Epitaxial growth of AlN films on Si substrates by ECR plasma assisted MOCVD under controlled plasma conditions in afterglow region

Wurtzite-type aluminum nitride (h-AIN) films were epitaxially grown on off- asis Si (111) substrates by electron-cyclotron-resonance plasma-enhanced me talorganic chemical vapor deposition (ECRMOCVD) using trimethylalminum (TMA ) and ammonia (NH3) as source gases. Plasma space potential in the growth c hamber was lowered by setting the magnetic field distribution as a mirror f ield. For the growth of h-AlN with excellent crystallinity on Si substrates , nitridation of the substrate surface, growth of a low-temperature (LT) bu ffer layer, and epitaxial growth of AlN films were performed under a min-or field condition in a growth chamber. Thermal nitridation at 1050 degrees C prior to the epitaxial growth appreciably improved the crystallinity of AW films. The growth of buffer layer at temperatures below 650 degrees C was not so effective for the improvement of the crystallinity and crystal orien tation of AIN epitaxial layer. The proportion of domain including stacking Faults and that whose c-axis was parallel to the substrate surface was very small (I-(0002)/(I(10-11) + I(10-11)) > 700), irrespective of the gas feed ratio of N source to Al source (NH3/TMA) during the epitaxial growth proce ss. Under a small gas feed ratio (NH3/TMA < 200), however, the diffraction peak intensities from the non-epitaxial domains became large. (C) 2000 Else vier Science B.V. All rights reserved.