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Search for a Metallic State on a GaAs Surface by Electrolytic Gating

Undergraduate #283
Discipline: Physics
Subcategory: Materials Science

Michelle R. Bundy - Saint Augustine's University
Co-Author(s): Gordon Stecklein and Paul Crowell, University of Minnesota, Minneapolis, MN



Electronics categorizes materials into three main types: metals, insulators, and semiconductors. A Metallic surface state was recently discovered in Si, our hypothesis is that it should also be discovered in GaAs because it has a higher mobility. We then designed an experiment in which we gate an ionic liquid to investigate if this induces a metallic surface state on insulating n -GaAs. We measured the resistivity from 2-300 K using the Physical Property Measurement System (PPMS) and a Van der Pauw method. Ohmic contacts to the GaAs substrate were created by annealing Ge/Au/Ni. In an experiment with 1×1016 cm-3 n-GaAs, applying a positive gate voltage increased the resistivity, but this increase in resistivity could not be reversed by applying a negative voltage. In experiments with 3×1015 cm-3 n-GaAs, the resistivity at 2 K decreased upon applying a gate voltage of 2 V, but there was not a monotonic change in resistivity with applied voltage. The temperature-dependence of the resistivity showed no evidence of a change from insulating to metallic behavior. But when a magnetic field was applied to a new sample of 3×1015 cm-3 n-GaAs, the resistivity was increased by a factor of 1000. This is a positive sign that with continuing further investigations using a magnetic field we will then be able to increase the bulk resistance high enough to induce a metallic surface state.

Funder Acknowledgement(s): This work was supported primarily by the National Science Foundation MRSEC and REU programs under Award Numbers DMR-1263062 and DMR1420013.

Faculty Advisor: Melton,

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This material is based upon work supported by the National Science Foundation (NSF) under Grant No. DUE-1930047. Any opinions, findings, interpretations, conclusions or recommendations expressed in this material are those of its authors and do not represent the views of the AAAS Board of Directors, the Council of AAAS, AAAS’ membership or the National Science Foundation.

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