Superconductivity in AuNiGe Ohmic contacts to a GaAs-based high mobility two-dimensional electron gas

Christopher Beauchamp; Stefanos Dimitriadis; James Nicholls; Lev Levitin; Andrew Casey; Patrick See; Graham  Creeth; Joanna Waldie; Ian  Farrer; Harvey  Beere; Dave  Ritchie; James Nicholls; John Saunders

doi:10.1063/5.0028217

Superconductivity in AuNiGe Ohmic contacts to a GaAs-based high mobility two-dimensional electron gas

Christopher Beauchamp, Stefanos Dimitriadis, James Nicholls, Lev Levitin, Andrew Casey, Patrick See, Graham Creeth, Joanna Waldie, Ian Farrer, Harvey Beere, Dave Ritchie, James Nicholls, John Saunders

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Abstract

To cool a high mobility two-dimensional electron gas (2DEG) at a GaAs-AlGaAs heterojunction to milliKelvin temperatures, we have fabricated low resistance ohmic contacts based on alloys of Au, Ni and Ge. The ohmic contacts have a typical contact resistance of R_C≈ 0.8 Ω at 4.2 K, which drops to 0.2 Ω below 0.9 K. Scanning electron microscope images establish that the contacts have the same inhomogeneous microstructure that has been observed in previous studies. Measurements of the contact resistance R_C, the four-terminal resistance along the top of a single contact, and the vertical resistance R_V , all show that there is a superconductor in the ohmic contact which can be turned completely normal with a magnetic field of 0.15 T. We briefly discuss how this superconductivity may be affecting the electrical transport measurements of 2DEGs, especially how it may hinder the cooling of electrons in a 2DEG below 0.1 K.

Original language	English
Article number	162104
Pages (from-to)	1-5
Number of pages	5
Journal	Applied Physics Letters
Volume	117
Issue number	16
Early online date	19 Oct 2020
DOIs	https://doi.org/10.1063/5.0028217
Publication status	Published - 19 Oct 2020

Keywords

semiconductor-semiconductor heterostructures
ohmic contact
SUPERCONDUCTIVITY

Access to Document

10.1063/5.0028217

Accepted ManuscriptAccepted author manuscript, 1.82 MB

Cite this

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title = "Superconductivity in AuNiGe Ohmic contacts to a GaAs-based high mobility two-dimensional electron gas",

abstract = "To cool a high mobility two-dimensional electron gas (2DEG) at a GaAs-AlGaAs heterojunction to milliKelvin temperatures, we have fabricated low resistance ohmic contacts based on alloys of Au, Ni and Ge. The ohmic contacts have a typical contact resistance of RC≈ 0.8 Ω at 4.2 K, which drops to 0.2 Ω below 0.9 K. Scanning electron microscope images establish that the contacts have the same inhomogeneous microstructure that has been observed in previous studies. Measurements of the contact resistance RC, the four-terminal resistance along the top of a single contact, and the vertical resistance RV , all show that there is a superconductor in the ohmic contact which can be turned completely normal with a magnetic field of 0.15 T. We briefly discuss how this superconductivity may be affecting the electrical transport measurements of 2DEGs, especially how it may hinder the cooling of electrons in a 2DEG below 0.1 K.",

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T1 - Superconductivity in AuNiGe Ohmic contacts to a GaAs-based high mobility two-dimensional electron gas

AU - Beauchamp, Christopher

AU - Dimitriadis, Stefanos

AU - Nicholls, James

AU - Levitin, Lev

AU - Casey, Andrew

AU - See, Patrick

AU - Creeth, Graham

AU - Waldie, Joanna

AU - Farrer, Ian

AU - Beere, Harvey

AU - Ritchie, Dave

AU - Nicholls, James

AU - Saunders, John

PY - 2020/10/19

Y1 - 2020/10/19

N2 - To cool a high mobility two-dimensional electron gas (2DEG) at a GaAs-AlGaAs heterojunction to milliKelvin temperatures, we have fabricated low resistance ohmic contacts based on alloys of Au, Ni and Ge. The ohmic contacts have a typical contact resistance of RC≈ 0.8 Ω at 4.2 K, which drops to 0.2 Ω below 0.9 K. Scanning electron microscope images establish that the contacts have the same inhomogeneous microstructure that has been observed in previous studies. Measurements of the contact resistance RC, the four-terminal resistance along the top of a single contact, and the vertical resistance RV , all show that there is a superconductor in the ohmic contact which can be turned completely normal with a magnetic field of 0.15 T. We briefly discuss how this superconductivity may be affecting the electrical transport measurements of 2DEGs, especially how it may hinder the cooling of electrons in a 2DEG below 0.1 K.

AB - To cool a high mobility two-dimensional electron gas (2DEG) at a GaAs-AlGaAs heterojunction to milliKelvin temperatures, we have fabricated low resistance ohmic contacts based on alloys of Au, Ni and Ge. The ohmic contacts have a typical contact resistance of RC≈ 0.8 Ω at 4.2 K, which drops to 0.2 Ω below 0.9 K. Scanning electron microscope images establish that the contacts have the same inhomogeneous microstructure that has been observed in previous studies. Measurements of the contact resistance RC, the four-terminal resistance along the top of a single contact, and the vertical resistance RV , all show that there is a superconductor in the ohmic contact which can be turned completely normal with a magnetic field of 0.15 T. We briefly discuss how this superconductivity may be affecting the electrical transport measurements of 2DEGs, especially how it may hinder the cooling of electrons in a 2DEG below 0.1 K.

KW - semiconductor-semiconductor heterostructures

KW - ohmic contact

KW - SUPERCONDUCTIVITY

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M3 - Article

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VL - 117

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EP - 5

JO - Applied Physics Letters

JF - Applied Physics Letters

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