Abstract
Experiments have been made using surface acoustic waves (SAW) propagating on two GaAs wafers on which a 2-dimensional hole system (2DHS) had been fabricated by MBE. On a GaAs (100) surface we used SAW at a frequency of 120 MHz. Amplitude modulation and a lock-in amplifier were used to measure the longitudinal and transverse acousto-electric voltages from a Hall-bar structure. Measurements have been made in a magnetic field up to 5 T and at temperatures between 4.2 and 2 K. A large longitudinal voltage was found which increased linearly with SAW power and 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 also used to measure the longitudinal and transverse acousto-electric voltages from a Hall-bar structure. The acousto-electric signals are compared with theoretical predictions using measured values of the longitudinal and transverse resistivity.
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