Direct measurement of acoustoelectric amplification parameters in surface acoustic waves

It is shown that classical formulae which describe acoustoelectric amplification can give the values of the coupling coefficient the dielectric relaxation frequency and the trapping parameters if one can measure the change of phase velocity as a function of the accelerating electric field. A method based on measurement of the phase velocity in the pulsed mode is proposed, which allows the direct determination of these various parameters. Experiments are performed on photoconducting CdS operating in the Rayleigh mode. The dielectric relaxation frequency omega c is not proportional to the semiconductor conductivity. The trapping time tau varies linearly from 10-9 s to 5*10-9 s with the conductivity in the range explored.