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The results of using molecular-beam epitaxy for growing piezoelectric AlN films on Si (111) substrates suitable for device applications are reported. The technological conditions for growth of stoichiometric AlN by controlling the surface reconstruction occurring under various thermodynamic conditions on the growth surface are determined. The films of the hexagonal polytype of AlN possess high crystalline perfection and an atomically smooth epitaxial surface. The mechanism for relaxation of the AlN crystal lattice over a distance of one monolayer from the heterojunction is found. It is demonstrated that the AlN film is piezoelectric. Investigations of the temporal characteristics of a SAW attest to a low level of scattering of the wave during propagation. The electromechanical coupling constant is measured in interdigital transducer geometry (λ=16 mm) and is found to be 0.07 % at a frequency f=286 MHz, in good agreement with the theoretical value for a 1.04-µm-thick AlN film.

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[2110]/Si[110] 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.