Pseudo-hysteretic behavior in semiconductor-superconductor junction

A recent work by Th. Schapers et alli [1] showed the coupling to a supercon ductor of the two-dimensional electron gas in a doped semiconductor heteros tructure. The presented I-V characteristic exhibits a hysteresis at the low -voltage range, similarly to I-V curves of other works for analogous struct ures. In this work we simulate that kind of junction using the Pereira-Nico lsky simplified model for superconductor-normal metal-superconductor system s applied to the dimensional parameters of that junction and the appropriat e Andreev density of states calculated for that doped semiconductor. We sho w that, at sub-gap voltages, pseudo-hysteresis is probably due to the kind of experimental set-rip used in the measurements and actually it hides a ne gative-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 simiconductor is heavily doped and exhibits a density of states within its energy gap. The negative derivative follows from the competition between th e increasing voltage and the decreasing of the allowed AR. Finally, we sugg est the kind of experiment should be done for avoiding that pseudo-hysteres is in those junctions.