Proximity effect in planar Superconductor/Semiconductor junction

TL;DR

This study investigates the low-temperature resistance behavior of a superconductor/semiconductor junction, revealing a coherence-induced resistance maximum and zero bias anomaly explained by reflectionless tunneling.

Contribution

It provides experimental evidence of reflectionless tunneling effects in a superconductor/semiconductor junction and compares results with existing theories to extract key physical parameters.

Findings

Resistance peaks around 300 mK due to coherent backscattering

Zero Bias Anomaly observed at low temperatures

Quantitative comparison with theoretical models

Abstract

We have measured the very low temperature (down to 30 mK) subgap resistance of Titanium Nitride (Superconductor, Tc = 4.6 K)/highly doped Silicon (Semiconductor) SIN junction (the insulating layer stands for the Schottky barrier). As the temperature is lowered, the resistance increases as expected in SIN junction. Around 300 mK, the resistance shows a maximum and decreases at lower temperature. This observed behavior is due to coherent backscattering towards the interface by disorder in Silicon ("Reflectionless tunneling"). This effect is also observed in the voltage dependence of the resistance (Zero Bias Anomaly) at low temperature (T<300 mK). The overall resistance behavior (in both its temperature and voltage dependence) is compared to existing theories and values for the depairing rate, the barrier resistance and the effective carrier temperature are extracted.