Effect of residual H 2 O on epitaxial AlN film growth on 4H-SiC by alternating doses of TMA and NH 3

Abstract An epitaxial AlN film was synthesized on 4H-SiC using alternate doses of trimethyl aluminum (TMA) and anhydrous ammonia (a-NH3) at 540 °C. The growth per cycle (GPC) at the temperature was limited to 0.27 A/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 A/cycle. The suppression of the OH group generation at 540 °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).