An epitaxial AlN film was synthesized on 4H-SiC using alternate doses of trimethyl aluminum (TMA) and anhydrous ammonia (a-NH3) at 540 degrees C. The growth per cycle (GPC) at the temperature was limited to 0.27 angstrom/cycle under the minute amount of residual H2O. The formation of an inert Al-O-Al bond generated by the recombinative desorption of two Al-OH species to produce H2O has been proposed as a possible reason for the low deposition rate. By eliminating any present moisture in the reactor system, the GPC increased to 1.5 angstrom/cycle. The suppression of the OH group generation at 540 degrees C made it possible to deposit nearly stoichiometric AlN film which has the crystallinity with the preferred orientation along the (0 0 0 1) direction on 4H-SiC templates. The measured RMS surface roughness was comparable to that achieved by molecular beam epitaxy (MBE). (C) 2014 Published by Elsevier B.V.