Conduction mechanism analysis in β-FeSi2/n-Si heterojunction through J–V–T measurement

Abstract

The p-type iron disilicide (β-FeSi2) semiconductor was formed at room temperature without heat treatment due to the superiority of the employed unbalanced magnetron sputtering technique on n-type crystalline silicon (n-Si), and conduction mechanism(s) of the resulting p-β-FeSi2/n-Si heterostructure was investigated by current density–voltage–temperature (J–V–T) measurement in darkness condition under vacuum after evaporation of both chromium (Cr) and gold (Au) metals as the front electrode. Two different current mechanisms seemed to be dominant on Cr/β-FeSi2/n-Si and Au/β-FeSi2/n-Si heterostructures, respectively. The transition of one mechanism to another occurred in a particular bias voltage range: between ∼3 kT/q and 0.3 V, the multistep tunneling capture emission (MSTCE) mechanism became dominant with an activation energy (EA) around 0.3 eV for both forward and reverse directions of bias and interpreted as an Fe impurity. Also, the reverse current density had a square-root dependence on reverse bias voltage, thus proposing generation current. In this frame, at an EA of 0.3 eV above the valance band edge denoted the efficient trap level for the recombination–generation mechanism in the β-FeSi2 semiconductor or at the interface of the β-FeSi2/Si heterojunction. Subsequently, as the second mechanism, space charge limited current (SCLC) started at a high forward bias voltage region (from 0.65 V to 1 V), where the power of the bias (m) changed from high to low value as the ambient temperature was increased (110 K to 380 K). A further increase in bias voltage (above 1 V) yielded a series resistance region where thermally activated current was observed, representing a conduction band offset, ΔEc. Its value was determined as 0.16 eV, consistent with the announced values in the literature.