Voltage controlled SAW velocity in GaAs/LiNbO3-hybrids

The combination of the electronic properties of semiconductor heterojunctio ns and the acoustic properties of piezoelectric materials yields very promi sing surface acoustic wave (SAW) hybrid systems. Quasi-monolithical integra tion of thin GaAs/InGaAs/AlGaAs-quantum well structures on LiNbO3 SAW devic es is achieved using the epitaxial lift-off (ELO) technique. The conductivi ty of the two-dimensional electron system in the quantum well, which can be controlled via field effect, modifies the velocity of the SAW. Due to the high electromechanical coupling coefficient of LiNbO3 a large phase shift c an be obtained. As an example for this new class of voltage-tunable single chip SAW devices, a voltage-controlled oscillator (VCO) is presented in whi ch the output frequency can be tuned by an applied gate voltage.