Piezoelectric Microbeam Resonators Based on Epitaxial AlxGa1−xAs Films

Piezoelectric resonators based on epitaxially-grown Al0.3Ga0.7As have been developed. The resonators are fabricated using a single crystal device structure, with differential doping used to create either piezoelectric or electrode regions. Constitutive layers consist of 0.5μm Si-doped Al0.3Ga0.7As acting as the top electrode layer, 1μm undoped Al0.3Ga0.7As as the piezoelectric layer, and 2μm Si-doped Al0.3Ga0.7As as both the structural and the bottom electrode layer. Resonator fabrication employs a 4 mask process combining inductively coupled plasma reactive-ion etching (ICP RIE) and a highly selective bulk GaAs wet etching process. The frequency response of fabricated beam resonators has been measured using laser Doppler vibrometery (LDV). Both cantilever and doubly-clamped beam resonators have been demonstrated, with fabricated resonators center frequencies showing excellent agreement compared to designed values. The transverse piezoelectric coupling coefficient d31 has also been measured as a function of beam orientation.