A 1 GHz SAW oscillator on epitaxial GaN/Si substrate: Toward co-integrated frequency sources

GaN is an attractive material for the fabrication of various integrated devices combining several physical effects (semi-conductors, piezoelectric and optic parts, etc.). This work is dedicated to the investigation of GaN for the fabrication of surface acoustic wave oscillators. The first functional two-port resonators have been designed and built on 1.8 μm thick GaN epitaxial layers grown on (111) Silicon. An analysis of the obtained results has been achieved and a set of elastic constants has been fitted to meet the best possible agreement between theory and experiments. Comparison between experimental and theoretical transfer functions has been also exploited to refine the estimation of the wave characteristics. An oscillator has been finally built using the obtained resonators to assess the interest of this material for this kind of application and to prepare future development on this basis.