Growth and Characterization of Thick Polycrystalline AlN Layers by HTCVD

Thick polycrystalline AlN layers were grown at low pressure using high temperature chemical vapor deposition (HTCVD). The experimental setup consists of a graphite susceptor heated by an induction coil surrounding a vertical cold wall reactor. The reactants used were ammonia (NH3) and aluminum chloride (AlClx) species formed in situ via chlorine (Cl-2) reaction with high purity aluminum wire. AlN films were deposited on a 55 mm diameter graphite susceptor between 1200 and 1600 degrees C. AlN layers have been characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, and electron backscattered diffraction. The influence of temperature on growth rate, surface morphology, grain size, and crystalline structure is presented. Growth rates of up to 230 mu m/h have been reached. A nonpolar preferred orientation of AlN films is stabilized at a higher temperature. The potential of investigation in this new range of experimental conditions, i.e., high temperature and high growth rate, as well as deposition of nonpolar AlN crystals, is very promising for epitaxial growth and extends the field of applications. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3536477] All rights reserved.