Two Kinds of Current Saturation on Non-Ohmic Behavior in CdS

Abstract

Two step current saturation was observed in CdS. The first saturation is well described by the theoretical calculation based on the classical sound amplification mechanism of TWT type introduced by White. While, the second saturation may be interpreted qualitatively by the quantum mechanical phonon amplification mechanism due to Cerenkov like radiation introduced by Yamashita and Nakamura. At the transients of the both saturations a current oscillation was observed. The oscillation of the first saturation may be caused by the natural vibration of the crystal, and the second damped one may be due to the non-linear property of the quantum mechanical coupling.