Quasi-monolithic GaAs/LiNbO3-hybrids for acoustoelectric applications

The combination of the electronic properties of a semiconductor heterojunction and the acoustic properties of a piezoelectric material yields very promising surface acoustic wave (SAW) hybrid systems. Quasi-monolithical integration of a thin GaAs/InGaAs/AlGaAs-quantum well structure on a LiNbO₃ SAW device is achieved using the epitaxial lift-off (ELO) technique. The active semiconductor layer system is removed from its substrate and transferred onto the LiNbO₃. The conductivity of the two dimensional electron system in the quantum well, which can be controlled via field effect, modifies the velocity of the surface acoustic waves. Due to the high electromechanical coupling coefficient of LiNbO₃ a change of the electrical boundary conditions produces a large phase shift. This leads to a new class of voltage tunable single-chip SAW devices, e,g., voltage controlled oscillators and tunable SAW delay lines