At low temperatures, an SSmS junction exhibits a diode-like behaviour with no current flowing at voltages below 2Δ/e. This can be explained by considering again figure 1.

Excluding the possibility of thermal excitations due to the low temperature, any electrons that are accelerated by a potential less than 2Δ/e will not be able to tunnel out of the semiconductor as there are no available states of equal energy in the superconductor due to the band gap. At higher temperatures however, ambient electrons are more likely to gain enough energy via thermal excitation to tunnel across the Schottky barrier into the free states of the superconductor, resulting in a significant current flow even at the lower voltages.

Figure 3: The current through a double junction device induced by a range of voltages for different semiconductor temperatures [1].