Andreev scattering and conductance enhancement in mesoscopic semiconductor-superconductor junctions

TL;DR

This paper models the transport properties of mesoscopic semiconductor-superconductor junctions, focusing on Andreev scattering and conductance enhancement, considering interface barriers and Fermi property mismatches in ballistic 2DEG systems.

Contribution

It provides a quantitative theoretical model for the conductance in ballistic 2DEG-superconductor interfaces with quantum point contacts, including effects of Schottky barriers and Fermi mismatches.

Findings

Model predicts conductance enhancement due to Andreev reflection.

Accounts for scattering effects at the interface.

Provides insights into optimizing contact quality.

Abstract

An inherent difficulty in studying mesoscopic effects in semiconductor--superconductor hybrid structures is the large Schottky barrier which often forms at the interface. A large technological effort has been invested in in improving the contact between the superconductor and the two-dimensional electron gas (2DEG) of a semiconductor heterostructure, and in recent years this has become possible for e.g. GaAs-Al, GaAs-In, and InAs-Nb junctions. This development motivates quantitative theoretical modeling of sample-specific transport properties. The aim of our work is to model the conducting properties of a ballistic 2DEG-S interfaces with a QPC in the normal region and also to take into account scattering due to a weak Schottky barrier and/or non-matching Fermi properties of the semiconductor and superconductor.