Epitaxial wurtzite aluminum nitride (AIN) films have been grown on (111) oriented silicon substrates by plasma-assisted solid source molecular beam epitaxy (MBE). The growth has been performed in the two-dimensional (2D) growth mode. Occuring surface reconstructions have been monitored by reflection of high-energy electron diffraction (RHEED). The films have been characterized by atomic force microscopy (AFM) and transmission electron microscopy (TEM). 2D grown films exhibit atomically smooth surfaces, are singlecrystalline and void of oriented domains. High-resolution (HR) TEM micrographs of the heterointerface show the presence of an interfacial atomic arrangement where (5:4) unit cells coincide along the AIN/Si direction.
Surface acoustic wave (SAW) properties of MBE-grown AIN(0001)/Si(ll1) have been studied for the first time. The AIN film exhibits very good piezoelectricity. The SAW time response indicates low scattering of the waves during their propagation. An electromechanical coupling coefficient (EMC) of 0.07% has been measured for the present interdigital transducer (IDT) geometry.