Influence of $$\hbox {Si}₃\hbox {N}₄$$ Si 3 N 4 layer on the electrical properties of Au/n-4H SiC diodes

In this study, the effect of (hbox {Si}₃hbox {N}₄) insulator layer on the electrical characteristics of Au/n-4H SiC diode was investigated. The current–voltage (({I{-}V})), capacitance–voltage (({C{-}V})) and conductance–voltage ((G/w{-}V)) measurements were carried out at room temperature condition. Under thermionic emission model, electrical parameters as zero-bias barrier height ((Phi _{mathrm{Bo}})), ideality factor (n), interface states ((D_{mathrm{it}})), and series ((R_{mathrm{s}})) and shunt ((R_{mathrm{sh}})) resistances were estimated from forward bias ({I{-}V}) analyses. The values of n and (Phi _{mathrm{Bo}}) were about 1.305 and 0.796 eV for metal–semiconductor (MS) rectifying diode, and 3.142 and 0.713 eV for metal–insulator–semiconductor (MIS) diode with the insertion of (hbox {Si}₃hbox {N}₄) layer, respectively. Since the values of n were greater than the unity, the fabricated diodes showed non-ideal ({I{-}V}) behaviour. The energy distribution profile of (D_{mathrm{it}}) of the diodes was calculated by taking into account of the bias dependence of the effective barrier height ((Phi _{mathrm{e}})) and (R_{mathrm{s}}). The obtained (D_{mathrm{it}}) values with (R_{mathrm{s}}) are almost one order of magnitude lower than those without (R_{mathrm{s}}) for two diodes. According to Cheung’s model, (R_{mathrm{s}}) were calculated and these values were found in increasing behaviour with the contribution of (hbox {Si}₃hbox {N}₄) insulator layer. In addition, the (J_{mathrm{R}}{-}V) plot behaviours with linear dependence between ln((J_{mathrm{R}})) vs. (V^0.5) indicated that the dominant conduction mechanism in the reverse bias region was Schottky effect for both MS and MIS diodes. In the room temperature ({C{-}V}) measurements, different from the results of MIS diode, the values of C for MS diode was observed in decreasing behaviour from ideality with crossing the certain forward bias voltage point ((sim ) (2.5 hbox {V})). The decrease in the negative capacitance corresponds to the increase of G / w.