THE SURFACE-CHEMISTRY OF ALUMINUM NITRIDE MOCVD ON ALUMINA USING TRIMETHYLALUMINUM AND AMMONIA AS PRECURSORS

The reactions of trimethylaluminum (TMAl) and ammonia (NH3) on gamma-a lumina were studied by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to explore their role in th e MOCVD growth of AlN. FTIR and XPS assignments of surface species wer e directly correlated based on data taken within the same high-vacuum system. The observed N(1s) binding energies of NH2, NH3, TMAl:NH3 addu ct, nitride, and dinitrogen complexes correlate well with the vibratio nal data. Coadsorption of TMAl and NH3 at room temperature leads to th e formation of Al-N covalent bonds, as indicated by the presence of br idge-bonded NH3 species. Upon heating to similar to 600 K and above, t he appearance of vibrational bands corresponding to AlN indicate the e mergence of extended Al-N networks on the surface; AlNN and HAlNN cont aminants are also formed. A reaction model for AlN film formation is p roposed.