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Growth and Transport Properties of Tunneling Barriers in Hts Devices

Published online by Cambridge University Press:  15 February 2011

G. J. Gerritsma ,
M. A. J. Verhoeven ,
R. Moerman ,
D. H. A. Blank  and
H. Rogalla
G. J. Gerritsma
Affiliation:
Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands
M. A. J. Verhoeven
Affiliation:
Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands
R. Moerman
Affiliation:
Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands
D. H. A. Blank
Affiliation:
Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands
H. Rogalla
Affiliation:
Applied Physics, University of Twente, P.O. Box 217, 7500 AE Enschede, Netherlands
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Abstract

In this contribution we will discuss the charge transport of ramp-type HTS Josephson junctions with a Ga-doped PBCO barrier layer. It will be demonstrated that in these junctions charge transport takes place via tunneling processes. The Cooper pairs tunnel directly, at least for T ≤ Tc/2, whereas the quasiparticles tunnel indirectly via localized states. By substituting Cu-chain atoms with Ga-atoms the density of localized states appear to be reduced, resulting in an increase in IcRn-product. Another way to increase this product is a reduction in barrier thickness. Growth studies by AFM of PBCO barriers on ramps indicate that below about 10 nm barriers become increasingly less homogeneous, and below about 6 nm pin holes are very likely to occur. This sets a lower limit on the useful barrier thickness. Presently critical-current densities up to 104 A/cm2 at 40 K, and IlR,-products up to 10 mV at 4.2 K are easily obtained.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 401: Symposium G – Epitaxial Oxide Thin Films II , 1995 , 287
Copyright
Copyright © Materials Research Society 1996

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