Location of the minimum of the differential tunneling resistance in a superconductor-degenerate semiconductor Schottky contact |
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Authors: | M.P. Lissitski A. Naddeo C. Nappi A. Tagliacozzo V.N. Gubankov R. Monaco M. Russo |
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Affiliation: | (1) Istituto di Cibernetica del Consiglio Nazionale delle Ricerche “E. Caianiello”, Pozzuoli (Napoli), Italy, IT;(2) INFM - Coherentia - Dipartimento di Scienze Fisiche Università Federico II, Napoli, Italy, IT;(3) Institute of Radio Engineering and Electronics of the Russian Academy of Sciences, Moscow, Russia, RU;(4) INFM-Dipartimento di Scienze Fisiche Università di Salerno, Salerno, Italy, IT |
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Abstract: | Measurements of differential resistance in a superconductor-degenerate semiconductor junction Nb - n + + GaAs at T = 1.6 K show close similarity to those for a conventional superconductor-insulator- normal metal junction, except for the position of the minimum which is located at 3.6 meV. Using a simple model for the charge screening at the Schottky barrier, we give an argument why this minimum is by far displaced with respect to the superconducting gap energy ( Δ g = 1.5 meV for bulk Nb). We argue that a rebuilding of the density of states takes place at the barrier, due to the imperfect metal screening in the degenerate semiconductor. Energy states close to the degenerate semiconductor Fermi energy are depleted at the barrier and are not available for tunneling, up to an energy Eg which adds to the superconducting gap Δ g . Received 11 November 2002 / Received in final form 21 February 2003 Published online 11 April 2003 RID="a" ID="a"e-mail: c.nappi@cib.na.cnr.it |
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Keywords: | PACS. 73.30.+y Surface double layers, Schottky barriers, and work functions – 73.40.-c Electronic transport in interface structures – 74.80.Fp Point contacts SN and SNS junctions |
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