Bistable Switch With Nonvolatile Memory States

Publishing Venue

IBM

Related People

Rutz, RF: AUTHOR

Abstract

Fig. A shows the current-voltage characteristics of a Si-AlN-SiC heterojunction bistable switching device, as shown in Fig. C, which device exhibits nonvolatile memory states. The bistable switching between nonvolatile states may be attributable to the trap filling phenomena of the Hovel bistable heterojunction switching devices. Such devices exhibit two well defined impedance states, somewhat symmetrical through the origin, akin to the characteristics shown in Fig. A. In Fig. A, the current I and voltage V represent the voltage and current taken at Si contact 25, in Fig. C, with respect to tungsten contact 7 which is held at a reference potential.

Bistable Switch With Nonvolatile Memory States

Fig. A shows the current-voltage characteristics of a Si-AlN-SiC heterojunction bistable switching device, as shown in Fig. C, which device exhibits nonvolatile memory states. The bistable switching between nonvolatile states may be attributable to the trap filling phenomena of the Hovel bistable heterojunction switching devices. Such devices exhibit two well defined impedance states, somewhat symmetrical through the origin, akin to the characteristics shown in Fig. A. In Fig. A, the current I and voltage V represent the voltage and current taken at Si contact 25, in Fig. C, with respect to tungsten contact 7 which is held at a reference potential.

A typical switching sequence for the Si-AlN-SiC heterojunction bistable switching device goes from a high-impedance state with a forward bias applied through a current-limiting resistor, as shown for example by the characteristic designated 1 in Fig. A, until a critical voltage V(f) is reached. The Si-AlN-SiC heterojunction device then switches to a low-impedance state, designated by line
3. The device will maintain this state for long periods of time (days) and at high temperatures (greater than 100 degrees C) of its own accord without the continued application of voltage thereacross. To return the heterojunction device to its high-impedance state a reverse bias is applied until a critical current I(R) is reached. These heterojunction switching devices also have intermediate impedance states. For example, as shown in Fig. A, the device may be switched from its high-impedance state at 1, to an intermediate state at 5, and thereafter switched to its low-impedance state at 3.

Fig. B shows apparatus which may be employed to fabricate the heterojunction bistable switch of refractory materials. The first step involves alloying either P or N high conducting SiC to a tungsten tab, which serves as one electrical terminal for the device.

The SiC with tungsten tab is then placed in a furnace arrangement a...