A TEM study of local non-uniformities in epitaxial 2H-AlN films on Si(111)substrate

Various non-uniformities of AIN thin films grown epitaxially on Si(111) sub strates by plasma-assisted molecular beam epitaxy (MBE) are characterised b y a combination of transmission electron microscopy (TEM), energy-dispersiv e X-ray spectroscopy (EDX), convergent-beam electron diffraction (CBED), an d secondary ion mass spectrometry (SIMS). Their appearance is interpreted i n relation to main growth parameters such as substrate temperature, nucleat ion temperature and the flux rate ratio of Al/N. It has been proved that al l films investigated are hexagonal and do not contain cubic AlN. We demonst rate that the creation of hillocks inside the layer of voids in the substra te and of crystals on top of the AlN film are closely connected with each o ther and depend mainly on the Al/N flux rate ratio. Domains of different po larity were found when increasing the nucleation temperature.