Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers

D. Gunnarsson, J.S. Richardson-Bullock, M.J. Prest, H. Q. Nguyen, A.V. Timofeev, V.A. Shah, T.E. Whall, E.H.C. Parker, D.R. Leadley, M. Myronov, M. Prunnila, James Richardson-Bullock

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The control of electronic and thermal transport through material interfaces is crucial for numerous micro and nanoelectronics applications and quantum devices. Here we report on the engineering of the electro-thermal properties of semiconductor-superconductor (Sm-S) electronic cooler junctions by a nanoscale insulating tunnel barrier introduced between the Sm and S electrodes. Unexpectedly, such an interface barrier does not increase the junction resistance but strongly reduces the detrimental sub-gap leakage current. These features are key to achieving high cooling power tunnel junction refrigerators, and we demonstrate unparalleled performance in silicon-based Sm-S electron cooler devices with orders of magnitudes improvement in the cooling power in comparison to previous works. By adapting the junctions in strain-engineered silicon coolers we also demonstrate efficient electron temperature reduction from 300 mK to below 100 mK. Investigations on junctions with different interface quality indicate that the previously unexplained sub-gap leakage current is strongly influenced by the Sm-S interface states. These states often dictate the junction electrical resistance through the well-known Fermi level pinning effect and, therefore, superconductivity could be generally used to probe and optimize metal-semiconductor contact behaviour.
Original languageEnglish
Article number17398
Pages (from-to)1-10
JournalScientific Reports
Publication statusPublished - 2015
MoE publication typeA1 Journal article-refereed


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