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-alumina were studied by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) to explore their role in the MOCVD growth of AlN. FTIR and XPS assignments of surface species were directly correlated based on data taken within the same high-vacuum system. The observed N(1s) binding energies of NH2, NH3, TMAl:NH3 adduct, nitride, and dinitrogen complexes correlate well with the vibrational data. Coadsorption of TMAl and NH3 at room temperature leads to the formation of Al-N covalent bonds, as indicated by the presence of bridge-bonded NH3 species. Upon heating to similar to 600 K and above, the appearance of vibrational bands corresponding to AlN indicate the emergence of extended Al-N networks on the surface; AlNN and HAlNN contaminants are also formed. A reaction model for AlN film formation is proposed.