Growth of thick AlN layers by High Temperature CVD (HTCVD)

To achieve AlN bulk growth, HTCVD chlorinated process is investigated. High growth rate and high crystalline quality are targeted for AlN films grown on (0001) alpha-Al2O3 and (0001) 4H or 6H SiC substrates between 1100 degrees C and 1750 degrees C. The precursors used are ammonia NH3 and aluminium chlorides AlClx species formed in situ by action of Cl-2 on high purity Al wire. Both influences of temperature and carrier gas on microstructure, crystalline state and growth rate are presented. Growth rates higher than 190 mu m.h(-1) have been reached. Thermodynamic calculations were carried out to understand the chemistry of AIN deposition. AIN layers were characterized by SEM and theta/2 theta X-Ray Diffraction. Their epitaxial relationships with substrates were deduced from pole figures obtained by X-Ray diffraction on a texture goniometer.