Acoustic Buildup in Photoconducting CdS Subjected to High rf Electric Fields

Long-term acoustic shear-wave buildup has been observed in the bulk of photoconducting CdS subjected to rf fields greater than 104 V/cm. Acoustic power was seen to grow for times as long as 5 msec in some samples. Short rf pulses applied within 1 msec after the long pulse generated much larger acoustic flux than if applied thereafter. At a given frequency the effect was a maximum in a certain conductivity region, this conductivity being higher the higher the frequency. A proposed explanation involves field quenching of the photoconductivity in narrow high-resistivity bands.