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Gunnarsson D, Richardson-Bullock JS, Prest MJ, Nguyen HQ, Timofeev AV, Shah VA, Whall TE, Parker EHC, Leadley DR, Myronov M, Prunnila M. Interfacial Engineering of Semiconductor-Superconductor Junctions for High Performance Micro-Coolers. Sci Rep 2015; 5:17398. [PMID: 26620423 PMCID: PMC4665018 DOI: 10.1038/srep17398] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 10/27/2015] [Indexed: 12/05/2022] Open
Abstract
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.
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Affiliation(s)
- D Gunnarsson
- VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland
| | | | - M J Prest
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - H Q Nguyen
- Low Temperature Laboratory (OVLL), Aalto University School of Science, PO Box 13500, FI-00076 Aalto, Finland
| | - A V Timofeev
- VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland
| | - V A Shah
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - T E Whall
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - E H C Parker
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - D R Leadley
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - M Myronov
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - M Prunnila
- VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT Espoo, Finland
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Abstract
ABSTRACTThe performance of many Si/SiGe devices, particularly those involving modulation doped quantum wells, will depend on the quality of the matrix and doping interfaces involved. These may be adversely affected by profile smearing of Ge and the dopant. A study of boron incorporation in SiGe, as a function of substrate temperature and Ge fraction, shows a marked difference in profile smearing for boron in Si and in the SiGe alloy. This is shown to be associated with a reduction in the temperature for transition from equilibrium to kinetically limited accumulation in the alloy.
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Abstract
ABSTRACTWe demonstrate the growth, by MBE, of high sheet density B delta layers in both Si and SiGe epitaxial layers. Double Crystal X-Ray Diffraction is shown to be a non-destructive method of characterising the width of very narrow (0.3 nm) delta layers and the sheet density of the activated B. The ability of delta layers to withstand high temperature anneals is considered and it is found that a 750 °C anneal for 1 hour broadens the delta layer to beyond the width required for carrier confinement.
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Powell AR, Kubiak RA, Whall TE, Parker EHC, Bowen DK. Residual Strain and Defect Analysis in as Grown and Annealed SiGe Layers. ACTA ACUST UNITED AC 2011. [DOI: 10.1557/proc-220-277] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
ABSTRACTIn this paper we address the problem of producing SiGe buffer layers of acceptable quality for the growth of symmetrically strained SiGe structures. Initially we consider SiGe layers grown to well beyond the metastable critical thickness and examine the degree of residual strain both as - grown and post anneal. The defect levels in metastable SiGe layers following high temperature anneal were also studied. A buffer layer was grown consisting of stacked metastable SiGe layers each of which is annealed in situ prior to the growth of the next layer and terminating with a 0.45 SiGe alloy. This produces nearly fully relaxed 1.15pim thick structures with threading dislocation densities of 4 × 106cm−2. Limited area growth on Si suggests that elastically relaxed material free of both threading and misfit dislocations can be produced.
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Graener H, Rosenberg M, Whall TE, Jones MRB. The low-temperature resistivity and Seebeck coefficient of fluorine-substituted magnetite. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642817908246380] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- H. Graener
- a Ruhr Universität Bochum , 4630 Bochum 1, West Germany
| | - M. Rosenberg
- a Ruhr Universität Bochum , 4630 Bochum 1, West Germany
| | - T. E. Whall
- b Physics Department , Portsmouth Polytechnic , Portsmouth , England
| | - M. R. B. Jones
- b Physics Department , Portsmouth Polytechnic , Portsmouth , England
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Whall TE, Salerno N, Proykova YG, Brabers VAM. The concentration dependences of the electrical conductivity and ordinary Hall coefficient of nickel ferrous ferrite. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642818608240639] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. E. Whall
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth, Hampshire , PO1 2DZ , England
| | - N. Salerno
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth, Hampshire , PO1 2DZ , England
| | - Y. G. Proykova
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth, Hampshire , PO1 2DZ , England
| | - V. A. M. Brabers
- b Department of Physics , Technical University , Den Dolech 2, 5600 , MB , Eindhoven , The Netherlands
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Whall TE, Yeung KK, Proykova YG, Braeaers VAM. The electrical conductivity and thermoelectric power of nickel ferrous ferrite Magnetic ordering effects. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642818408238893] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. E. Whall
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , PO1 2DZ , England
| | - K. K. Yeung
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , PO1 2DZ , England
| | - Y. G. Proykova
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , PO1 2DZ , England
| | - V. A. M. Braeaers
- b Department of Physics , Technical University , Den Dulech 2, 5600 MB , Eindhoven , The Netherlands
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Affiliation(s)
- P. J. Phillips
- a Department of Physics , University of Wanvick , Gibbet Hill Road, Coventry , CV4 7AL , England
| | - T. E. Whall
- a Department of Physics , University of Wanvick , Gibbet Hill Road, Coventry , CV4 7AL , England
| | - V. A. M. Brabers
- b Department of Physics , University of Technology , Den Dolech 2, 5600 MB , Eindhoven , The Netherlands
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Whall TE, Salerno N, Proykova Y, Mirza KA, Mazen S. The electrical conductivity and thermoelectric power of lithium ferrite in the vicinity of the order-disorder transition temperature. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642818608240648] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. E. Whall
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , Hampshire , PO1 2DZ , England
| | - N. Salerno
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , Hampshire , PO1 2DZ , England
| | - Y. Proykova
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , Hampshire , PO1 2DZ , England
| | - K. A. Mirza
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , Hampshire , PO1 2DZ , England
- b School of Mathematical and Physical Sciences, University of Sussex , Falmer, Sussex , England
| | - S. Mazen
- a Department of Physics , Portsmouth Polytechnic , Park Building, King Henry I Street, Portsmouth , Hampshire , PO1 2DZ , England
- c Department of Physics , University of Zagazig , Egypt
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Whall TE, Yeung KK, Proykova YG, Brabers VAM. Electrical conductivity and thermoelectric power of nickel ferrous ferrite Variable-range hopping and the Coulomb gap. ACTA ACUST UNITED AC 2006. [DOI: 10.1080/13642818608236866] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- T. E. Whall
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , King Henry I Street, Portsmouth , PO1 2DZ , England
| | - K. K. Yeung
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , King Henry I Street, Portsmouth , PO1 2DZ , England
| | - Y. G. Proykova
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , King Henry I Street, Portsmouth , PO1 2DZ , England
| | - V. A. M. Brabers
- b Department of Physics , Technical University , Den Dolech 2, 5600 , MB Eindhoven , The Netherlands
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Affiliation(s)
- T. E. Whall
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , Park Building, King Henry I St, Portsmouth , PO1 2DZ , England
| | - N. Salerno
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , Park Building, King Henry I St, Portsmouth , PO1 2DZ , England
| | - Y. G. Proykova
- a Department of Applied Physics and Physical Electronics , Portsmouth Polytechnic , Park Building, King Henry I St, Portsmouth , PO1 2DZ , England
| | - V. A. M. Brabers
- b Department of Physics , Technical University , Den Dolech , 5600 MB , Eindhoven , The Netherlands
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Affiliation(s)
- T. E. Whall
- a Department of Physics , Portsmouth Polytechnic , King Henry I Street, Portsmouth , PO1 2DZ , England
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Kiatgamolchai S, Myronov M, Mironov OA, Kantser VG, Parker EHC, Whall TE. Mobility spectrum computational analysis using a maximum entropy approach. Phys Rev E Stat Nonlin Soft Matter Phys 2002; 66:036705. [PMID: 12366296 DOI: 10.1103/physreve.66.036705] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2002] [Indexed: 05/23/2023]
Abstract
A method to calculate a smooth electrical conductivity versus mobility plot ("mobility spectrum") from the classical magnetoconductivity tensor in heterogeneous structures with the help of a "maximum entropy principle" has been developed. In this approach the closeness of the fit and the entropy of the mobility spectrum are optimized. The spectrum is then the most probable one with the least influence of the personal bias of the investigator for any given set of experimental data and is maximally noncommittal with regard to the unmeasured data. The advantages of the maximum entropy mobility spectrum analysis as compared to the conventional mobility spectrum analysis are demonstrated using a synthetic dataset.
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Affiliation(s)
- S Kiatgamolchai
- Department of Physics, University of Warwick, Coventry CV4 7AL, U.K
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Dorozhkin SI, Emeleus CJ, Whall TE, Landwehr G. Tuning of the quantum-Hall-effect-state-insulator transition by tilting of magnetic field. Phys Rev B Condens Matter 1995; 52:11638-11641. [PMID: 9980289 DOI: 10.1103/physrevb.52.r11638] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Wong SL, Kinder D, Nicholas RJ, Whall TE, Kubiak R. Cyclotron-resonance measurements on p-type strained-layer Si1-xGex/Si heterostructures. Phys Rev B Condens Matter 1995; 51:13499-13502. [PMID: 9978153 DOI: 10.1103/physrevb.51.13499] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Paul DJ, Cleaver JR, Ahmed H, Whall TE. Cotunneling of holes in silicon-based structures. Phys Rev B Condens Matter 1994; 49:16514-16517. [PMID: 10010803 DOI: 10.1103/physrevb.49.16514] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Emeleus CJ, Whall TE, Smith DW, Mattey NL, Kubiak RA, Parker EH, Kearney MJ. Observation of novel transport phenomena in a Si0.8Ge0.2 two-dimensional hole gas. Phys Rev B Condens Matter 1993; 47:10016-10019. [PMID: 10005099 DOI: 10.1103/physrevb.47.10016] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Kubiak RAA, Newstead SM, Leong WY, Houghton R, Parker EHC, Whall TE. The electrical properties of doped silicon, grown by Molecular-Beam-Epitaxy (MBE). ACTA ACUST UNITED AC 1987. [DOI: 10.1007/bf00620599] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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