THE ACOUSTOELECTRIC EFFECT IN THE 2-D HOLE SYSTEM USING SAW

Experiments have been made using surface acoustic waves (SAW) propagat ing on two GaAs wafers on which a 2- dimensional hole system (2DHS) ha d been fabricated by MBE. On a GaAs (100) surface we used SAW at a fre quency of 120 MHz. Amplitude modulation and a lock-in amplifier were u sed to measure the longitudinal and transverse acousto-electric voltag es from a Hall-bar structure. Measurements have been made in a magneti c field up to 5 T and at temperatures between 4.2 and 2 K. A large lon gitudinal voltage was found which increased linearly with SAW power an d also increased with applied magnetic field. We have also used a GaAs (311) wafer and SAW at a frequency of 113 MHz. Using pulse modulation , measurements have been made of the SAW attenuation and dispersion as a function of magnetic field up to 13 T and at temperatures below 100 mK. Square wave amplitude modulation and a lock-in amplifier were als o used to measure the longitudinal and transverse acousto-electric vol tages from a Hall-bar structure. The acousto-electric signals are comp ared with theoretical predictions using measured values of the longitu dinal and transverse resistivity.