Polytype control and properties of AIN on silicon

In this paper we report on the optical and structural characterisation of cubic polytype AlN thin films on 3C-SiC/Si(111) pseudo-substrates prepared by carbonisation. We have found that 3C-AlN phase can be stabilised on the "waved" 3C-SiC(111) surface by polytype replication. On the other hand, 2H-AlN was grown on atomically smooth surfaces. X-ray diffraction and transmission electron microscopy imply that the cubic AlN was grown along with hexagonal inclusions up to 20%. Spectroscopic ellipsometry in the infrared region show the typical phonon lines for the two polytypes. The appearance of the TO phonon at 646 cm(-1) confirms the existence of 3C-AlN. In the ultraviolet region the critical points in the band structure m ere identified. For 3C- and 2H-AlN the first direct transition at the Gamma-point was determined to be at 5.74 eV and 6.16 eV, respectively. No indirect transition at lower energies was detected.