GeSbTe - Threshold Switching

Threshold Switching

Threshold switching occurs when GeSbTe goes from a high resistive state to a conductive state at the threshold voltage. This can be seen from the current-voltage (IV) plot, where current is very low in the amorphous state at low voltage until threshold voltage is reached. Current increases rapidly after the voltage snapback. The material is now in the amorphous "ON" state, where the material is still amorphous, but in a pseudo- crystalline electric state. In crystalline state, the IV characteristics is ohmic. There had been debate on whether threshold switching was an electrical or thermal process. There were suggestions that the exponential increase in current at threshold voltage must have been due to generation of carriers that vary exponentially with voltage such as impact ionization or tunneling.