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Browse Prior Art Database

Superconductor-Semiconductor Proximity Effect Devices

IP.com Disclosure Number: IPCOM000102176D
Original Publication Date: 1990-Nov-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 4 page(s) / 115K

Publishing Venue

IBM

Related People

Jackson, TN: AUTHOR [+2]

Abstract

Disclosed is a new class of devices based on the proximity effect between superconductors and semiconductors.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Superconductor-Semiconductor Proximity Effect Devices

       Disclosed is a new class of devices based on the
proximity effect between superconductors and semiconductors.

      Fig. 1 shows one implementation, consisting of a thin (N 5 nm)
superconducting film (e.g., Nb) deposited and patterned on a semicon
ductor substrate.  A doped region is provided in the semiconductor
under the superconductor and electrical contact is provided to this
region.  The surrounding semiconductor is either semi-insulating or
is doped opposite to the first doped region.  If needed, protection
is provided to the thin superconductor to avoid degradation. By
varying the bias applied between the doped semiconductor region and
the superconducting film, the thickness of the interfacial Schottky
barrier can be varied.  This allows the superconducting critical
temperature and critical current to be varied.  This allows great
sensitivity; for operating temperatures very near the transition
temperature, the bias can be varied slightly to move the transition
temperature through the sample temperature.  A similar threshold
effect is achieved by supply ing a current very near the critical
current and varying the semiconductor bias to vary the transition
temperature.  A wide range of choices are possible for the
semiconductor, allowing the barrier height (and thickness) of the
Schottky barrier to be varied over a wide range.

      Fig. 2 shows a second proximity effect device.  In this case a
superconductor (e.g., Nb) is deposited on a p-type semiconductor for
which the surface and interface Fermi level is pinned in the
conduction band (e.g., InAs or InSb). An inversion layer will be
formed at the superconductor-semiconductor interface, and the number
of electrons in this inversion layer can be varied over a wide range
by varying the bias between the superconductor and the p-type
semiconductor.

      A similar device can be made using a superconductor deposited
on a thin insulator (N 5-20 nm) on a semiconductor (e.g., SiO2 on
Si), as shown in Fig. 3.  For semiconductor-insulator systems that do
not pin strongly the region under the insulator can be varied from
one doping type through depletion to inversion.  In this case the
situation is similar to a superconductor separate...