International Business Machines Corporation

Werner Baechtold

Pierre L Gueret

Christoph S Harder

Hans P Wolf

Alexis Baratoff

The transistor comprises two electrodes, (source (22) and drain (23), with a semiconductor tunnel channel (21A, 21B) arranged therebetween. A gate (24) for applying control signals is coupled to the channel. The semiconductor channel consists of a plurality of regions differing in their current transfer characteristics: contact regions (21c), connected to the source and drain electrodes, and a tunneling region (21t) arranged between the contact regions. The energy of free carriers in the contact regions differs from the energy of the conduction band or the valence band of the tunneling region which forms a low energy tunnel barrier the height (.DELTA.E) of which can be modified by control signals applied to the gate. The operating temperature of the device is kept sufficiently low to have the tunnel current through the barrier outweigh currents of thermionically excited carriers.

Low temperature tunneling transistor

For storing digital data e.g. in magnetic vortex shift registers, a single flux quantum vortex is injected into a superconductive layer by a vortex generator consisting of an emitter and a transfer station. The emitter generates a pool of vortices. The transfer station upon a signal transfers one single vortex at the time. In a particular embodiment, the transfer station consists of a Josephson interferometer at the entrance of a transfer channel. Switching of the interferometer passes a flux vortex from a vortex pool to a shifting and storage apparatus. Other embodiments do not use interferometers but include transfer channels with separation corners and vortex spacing means which insure that upon application of appropriate signals one and only one vortex is passed from the vortex pool to the shifting and storage means.

Magnetic vortex generator with a vortex pool and single vortex transfer

Two Josephson gates are connected in series to a low impedance voltage source. Each junction is bridged by a load impedance. The feed voltage is maintained in the order of the gap voltage which corresponds to the voltage drop across a Josephson junction when it is in its single-particle-tunneling state. Therefore, only one out of both Josephson elements can exist in the voltage state at a time, and the other junction is forced to assume the superconducting pair-tunneling state. In its symmetric form, the basic circuit can be used as flip-flop or storage means. If asymmetric, the basic circuit shows monostable switching behavior, and it can be used as logic gate. Circuit asymmetry can be caused either by design using different junction areas or electrically by proper bias control currents applied to either or both gates of the basic circuit. The degree of symmetry or asymmetry can even be shifted with electrical means. AND and OR gates and inverting embodiments which perform logic NAND and NOR functions are shown.

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Langnau, Switzerland

Werner Baechtold