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Insulator With Magnetic Impurities for Suppressing Josephson Currents

IP.com Disclosure Number: IPCOM000044119D
Original Publication Date: 1984-Nov-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Muller, KA: AUTHOR

Abstract

In a cryogenic tunneling transistor consisting of a sandwich-like structure of three electrodes separated by two insulating layers that permit tunneling, the insulating layers are doped with magnetic impurities in order to suppress Josephson currents which may otherwise couple the electrodes. Fig. 1 schematically illustrates the three-port structure. Fig. 2 represents the energy band diagram of the device. Two insulating layers I are arranged between source S and gate G electrodes and between gate and drain D electrodes, respectively. Source/drain voltage VSD is provided to electrodes S and D, whereas the signals VG for controlling the tunnel current through the device are applied to electrode G. Control is by lowering or increasing the height of the tunnel barrier (in the order of a few meV) between S and D.

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Insulator With Magnetic Impurities for Suppressing Josephson Currents

In a cryogenic tunneling transistor consisting of a sandwich-like structure of three electrodes separated by two insulating layers that permit tunneling, the insulating layers are doped with magnetic impurities in order to suppress Josephson currents which may otherwise couple the electrodes. Fig. 1 schematically illustrates the three-port structure. Fig. 2 represents the energy band diagram of the device. Two insulating layers I are arranged between source S and gate G electrodes and between gate and drain D electrodes, respectively. Source/drain voltage VSD is provided to electrodes S and D, whereas the signals VG for controlling the tunnel current through the device are applied to electrode G. Control is by lowering or increasing the height of the tunnel barrier (in the order of a few meV) between S and D. All three electrodes are superconducting (S), the gate electrode material having a band gap W2 larger than that of source S and drain D (both W1). The operation of the device depends on quasi particle tunneling. However, with thin normal insulator or semiconductor layers I a Josephson current Is will flow through the SIS "junctions", thereby electrically coupling the electrodes. Is needs to be suppressed. This can be done in a controlled manner by doping the insulator with magnetic impurities, such as Fe3+, in Al23+O3, Mn2+ in Mg2+O, etc. To suppress Is effectively, the doping has to be su...