Transport properties of Pr0.7Ca0.3MnO3/Nb:SrTiO3 heterojunctions

Current–voltage (J–V) characteristics of epitaxial hetero-junctions composed of Pr0.7Ca0.3MnO3 and Nb:SrTiO3 were studied under forward and reversed bias conditions. Detailed analysis showed that the J–V characteristics of these heterojunctions can be well-fitted by the thermally-assisted tunnelling model. While the dielectric constant of Nb:SrTiO3 extracted under the forward bias was about one order of magnitude smaller than that of bulk SrTiO3, the value obtained under reverse bias was very close to that of the bulk SrTiO3. The result can be explained by the existence of an interface layer on the Nb:SrTiO3 substrate with a smaller effective dielectric constant. The current finding suggested that the properties of interface layer should be taken into account in order to accurately simulate the J–V characteristics of such heterojunctions.