Molecular-beam epitaxy of a strongly lattice-mismatched heterosystem AlN/Si(111) for application in SAW devices

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