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 f ilms on Si (111) substrates suitable for device applications are reported. The technological conditions for growth of stoichiometric AlN by controllin g the surface reconstruction occurring under various thermodynamic conditio ns on the growth surface are determined. The films of the hexagonal polytyp e of AlN possess high crystalline perfection and an atomically smooth epita xial surface. The mechanism for relaxation of the AlN crystal lattice over a distance of one monolayer from the heterojunction is found. It is demonst rated that the AlN film is piezoelectric. Investigations of the temporal ch aracteristics of a SAW attest to a low level of scattering of the wave duri ng propagation. The electromechanical coupling constant is measured in inte rdigital transducer geometry (lambda=16 mm) and is found to be 0.07 % at a frequency f=286 MHz, in good agreement with the theoretical value for a 1.0 4-mu m-thick AlN film. (C) 1999 American Institute of Physics. [S1063-7826( 99)01911-0].