An analysis of current instabilities in semi-insulating piezoelectric crystals

Abstract
The conditions for current oscillation in a semi-insulating piezoelectric crystal with nonuniform carrier concentration are obtained using a simplified electron-phonon interaction law and the Weinreich momentum relationship. Start-oscillation conditions are then obtained as a function of the applied field, the carrier concentration ratio in the two parts of the crystal and the ratio of their lengths. The calculations are compared with experimental results and it is concluded that much of the observed behavior can be predicted qualitatively by this simple analysis.