Proximity effect in planar Superconductor/Semiconductor junction

We have measured the very low temperature (down to 30mK) subgap resistance of Titanium Nitride (Superconductor, Tc = 4.6K)/highly doped Silicon (Semiconductor) SIN junction (the insulating layer I stands for the Schottky barrier). As the temperature is lowered below the gap, the resistance increases as expected in SIN junction. Around 300mK, the resistance shows a maximum and decreases at lower temperature. This observed behavior is due to coherent backscattering towards the interface by disorder in the Silicon (“Reflectionless tunneling”). This effect is also observed in the voltage dependence of the resistance (Zero Bias Anomaly) at low temperature (T < 300mK). 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.