Circuit applications of Ovonic switching devices

A review of application circuits for two-terminal amorphous semiconductor switching devices encompassing both the threshold and memory switches is presented, including brief discussions of device electrical and structural characteristics. The most useful electrical properties of these devices are seen to be the threshold turn-on characteristic and the high on-to-off impedance ratio, in the range 10
³
to 10
⁷
. Particular emphasis is placed on those applications requiring the versatility of thin-film processing techniques to show feasibility. Also, recent device and circuit developments utilizing a thin-film four-terminal switching structure to obtain input/ output circuit isolation are discussed.