© 2020, Springer Science+Business Media, LLC, part of Springer Nature.In this work, Au/4H–SiC Schottky diodes with different Bi2O3–x:PVA (x = Sm, Sn, Mo) thin insulator interface layer were produced for the fabrication of metal/insulator/semiconductor (MIS) structures. The effect of different Bi2O3–x:PVA interfacial layer deposited between metal and semiconductor on important optical and electrical parameters of Schottky diodes was investigated. The main electrical parameters of the prepared structures such as the saturation current (I0), the barrier height (ΦB0), ideality factor (n), and series and shunt resistance (Rs and Rsh) were obtained from the I‒V characteristics. The discrepancies in these parameters can be ascribed to the use of different nanomaterials as an interlayer. Moreover, the values of n, ΦB0, and Rs were also extracted by using Cheung and Norde functions and obtained results were compared with each other. The energy dependence of interface states [Nss vs (Ec − Ess)] was investigated by taking into account the voltage dependence of Φe(V) and n(V). In addition, Ln(I)–Ln(V) plots were drawn to specify the possible current transport mechanisms of the prepared structures. Experimental results show that the Schottky structures with (Bi2O3–Sn:PVA) and (Bi2O3–Sm:PVA) interlayers yield higher RR and Rsh values and lower Io values. This provides an evidence to performance increase in MS structures.