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Is the `Finite Bias Anomaly' in planar GaAs-Superconductor junctons caused by point-contact like structures?

S. Chaudhuri·P. F. Bagwell·D. McInturff·J. C. P. Chang·S. Paak·M. R. Melloch·J. M. Woodall·T. M. Pekarek·B. C. Crooker
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Abstract

We correlate transmission electron microscope (TEM) pictures of superconducting In contacts to an AlGaAs/GaAs heterojunction with differential conductance spectroscopy performed on the same heterojunction. Metals deposited onto a (100) AlGaAs/GaAs heterostructure do not form planar contacts but, during thermal annealing, grow down into the heterostructure along crystallographic planes in pyramid-like `point contacts'. Random surface nucleation and growth gives rise to a different interface transmission for each superconducting point contact. Samples annealed for different times, and therefore having different contact geometry, show variations in $dI/dV$ characteristic of ballistic transport of Cooper pairs, wave interference between different point emitters, and different types of weak localization corrections to Giaever tunneling. We give a possible mechanism whereby the `finite bias anomaly' of Poirier et al. (Phys. Rev. Lett., {\bf 79}, 2105 (1997)), also observed in these samples, can arise by adding the conductance of independent superconducting point emitters in parallel.

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S. Chaudhuri, P. F. Bagwell, D. McInturff, J. C. P. Chang, S. Paak, M. R. Melloch, J. M. Woodall, T. M. Pekarek, B. C. Crooker. 1999-04-16. Is the `Finite Bias Anomaly' in planar GaAs-Superconductor junctons caused by point-contact like structures?. https://doi.org/10.1006/spmi.1999.0758

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