Study of mesoscopic phenomena at superconductor-semiconductor interfaces
Abstract
Mesoscopic Superconductivity has attracted a lot of attention since the early 90's, both from the viewpoint of answering many fundamental questions associated with the Josephson and Giaever effects associated with the devices and from the possible prospects of achieving faster switching capability than the conventional tunnel junction SIS structures. With the advancement in material growth techniques, processing and lithography, it is possible today to fabricate semiconductor devices of dimensions of the order of a few Fermi wavelengths, where the electrons behave essentially like a wave when cooled to below 4.2K. Hence these devices are ideal to study quantum interference phenomena and when they have superconducting contacts, we observe many new and interesting mesoscopic physics due to Andreev reflection at the contacts. This research carries out experimental and theoretical study of mesoscopic phenomena at different Superconductor-Semiconductor interfaces. A barrier free interface is essential for high probability of Andreev reflection and therefore different fabrication issues have been investigated to achieve this purpose. Different semiconductor-superconductor combinations have been explored and interesting mesoscopic effects reported. When a SNS junction of length less than the phase breaking length is fabricated, then the junction becomes a mesoscopic Josephson junction. Using a gate to control the critical current, it is possible to observe many interesting unexplored mesoscopic phenomena. InAs heterostructures and LT GaAs heterostructures can be considered good candidates for the normal metal.
Degree
Ph.D.
Advisors
Bagwell, Purdue University.
Subject Area
Electrical engineering
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