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Proximity Effect-Controlled Superconducting Tunnel Junction Transistor

IP.com Disclosure Number: IPCOM000106857D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 73K

Publishing Venue

IBM

Related People

Kleinsasser, AW: AUTHOR

Abstract

Disclosed is a superconducting transistor which uses modulation of the strength of the proximity effect between a semiconductor and a superconducting tunnel junction electrode in order to vary the electrical characteristics of the junction. Three-terminal devices based on controlling the current-voltage characteristics of a superconductor-insulator-superconductor tunnel junction depend upon perturbing an electrode far from equilibrium, resulting in heating and slow response. The disclosed device avoids this difficulty by using the proximity effect to alter the properties of an electrode of a tunnel junction without perturbing it from equilibrium.

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Proximity Effect-Controlled Superconducting Tunnel Junction Transistor

      Disclosed is a superconducting transistor which uses modulation
of the strength of the proximity effect between a semiconductor and a
superconducting tunnel junction electrode in order to vary the
electrical characteristics of the junction.  Three-terminal devices
based on controlling the current-voltage characteristics of a
superconductor-insulator-superconductor tunnel junction depend upon
perturbing an electrode far from equilibrium, resulting in heating
and slow response.  The disclosed device avoids this difficulty by
using the proximity effect to alter the properties of an electrode of
a tunnel junction without perturbing it from equilibrium.

      The invention is schematically illustrated in the Figure.  The
superconducting electrodes are part of a
superconductor-insulator-superconductor junction deposited on a
semiconductor heterostructure.  The lower superconducting electrode
is no thicker than a few times the superconducting coherence length
for the material.  For a Nb film, this means no more than 10-20 nm
thick; for a  YBa sub 2 Cu sub 3 O sub 7-x
 (or other cuprate superconductor), no more than a few nm thick.  The
heterostructure is a pn junction or Schottky diode.  The top layer
could be n-type Si or InGaAs.  The lower layer could be either p-type
or heavily-doped material with a smaller bandgap (SiGe in the case of
Si or In-rich InGaAs in the InGaAs case, resulti...