High-frequency surface acoustic wave devices based on epitaxial Z-LiNbO3 layers on sapphire

Abstract

Filter market demands push the development of new piezoelectric materials to address the modern telecommunication challenges. Combining composite wafers with an epitaxial piezoelectric layer and a said high velocity and acoustic quality substrate is a promising way to answer those demands. However, the fabrication of high-quality LiNbO3 films with reproducible physical properties is complicated by the difficulty in controlling volatile Li2O incorporation into the film and of measuring its composition. So far, large-scale production of films with physical properties suitable for the targeted applications is not available. In this paper, lithium niobate films with controlled nonstoichiometry were deposited by means of pulsed injection metalorganic vapor phase deposition. We have demonstrated a high acoustical performance for surface acoustic wave devices operating in the frequency range of 3.7 GHz up to 5.3 GHz and based on grown epitaxial Z-axis oriented LiNbO3 films on sapphire. An electromechanical coupling of 8% for the Rayleigh wave at 5.3 GHz was demonstrated experimentally.