Charge transport in superconducting MoRe–Si(W)–MoRe heterostructures with hybrid semiconductor barrier containing metal nanoclusters

Abstract

Thin-film MoRe–Si(W)–MoRe heterostructures consisting of superconducting electrodes (molybdenum-rhenium alloy) and a hybrid semiconductor tunnel barrier consisting of a nanosized silicon layer with tungsten nanoclusters were fabricated and experimentally studied. Current-voltage characteristics of the heterostructures were measured in a wide voltage range from −900 to 900 mV and at temperatures from 4.2 to 8 K, under applied magnetic fields and microwave irradiation. We argue that the temperature dependences of the superconducting critical current and normal-state resistance of the heterostructures might indicate the presence of Coulomb blockade regime, resonant tunneling and resonant-percolation transport mechanism in the junctions, depending on the tungsten content in the hybrid barrier and the applied bias voltage. The measured characteristics suggest that for the superconducting current exceeding some critical value, the phase-slip centers of the superconducting order parameter are formed in the tungsten clusters.