The electrostrictor—A new type of electromechanical semiconductor oscillator

An investigation is carried out of unexpected electrical oscillations generated across germanium crystals which are subjected to strong electric fields; the latter are obtained by the application of a current pulse through a small area metallic electrode. The oscillations are found to be of electromechanical nature; i.e., it is shown that the electrical oscillations are accompanied with mechanical oscillations of the same frequency and, furthermore, that the latter have a definite phase relation with the former. The frequency of oscillation is identified as the mechanical natural frequency of vibration of the crystal-electrode combination. The electromechanical coupling in germanium is found to be due to a large electrostrictive property of this crystal. The electro-mechanical regenerative path responsible for the generation of oscillation is postulated to be due to the elastroresistance effect in germanium. Finally an electromechanical equivalent circuit for this novel device, called henceforth the electrostrictor, is derived predicting most of its experimentally observed characteristics.