Pseudo-hysteretic behavior in semiconductor-superconductor junction

Abstract

A recent work by Th. Schäpers et alli [1] showed the coupling to a superconductor of the two-dimensional electron gas in a doped semiconductor heterostructure. The presented I–V characteristic exhibits a hysteresis at the low-voltage range, similarly to I–V curves of other works for analogous structures. In this work we simulate that kind of junction using the Pereira-Nicolsky simplified model for superconductor-normal metal-superconductor systems applied to the dimensional parameters of that junction and the appropriate Andreev density of states calculated for that doped semiconductor. We show that, at sub-gap voltages, pseudo-hysteresis is probably due to the kind of experimental set-up used in the measurements and actually it hides a negative-differential-resistance behavior. The negative derivative in the I–V characteristic is a direct consequence of the multiple Andreev reflection (AR) mechanisms at the superconductor-semiconductor interfaces because the semiconductor is heavily doped and exhibits a density of states within its energy gap. The negative derivative follows from the competition between the increasing voltage and the decreasing of the allowed AR. Finally, we suggest the kind of experiment should be done for avoiding that pseudo-hysteresis in those junctions.