We investigated the temperature dependence of carrier transport and resistance switching of $\mathrm{Pt}/\mathrm{Sr}{\mathrm{Ti}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ Schottky junctions in the temperature range 80–400 K by measuring the current-voltage (I-V) characteristics and the frequency dependence of the capacitance-voltage (C-V) characteristics. The I-V curves displayed a high degree of hysteresis, known as the colossal electroresistance (CER) effect, and their temperature dependence showed an anomalous behavior, i.e., the magnitude of the hysteresis increased with decreasing $T$. The experimental results were analyzed by taking into account the temperature and electric-field dependence of the relative permittivity of $\mathrm{Sr}{\mathrm{Ti}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ as well as the inhomogeneity of the Schottky barrier height (SBH) (a model in which two parallel current paths coexist in the Schottky barrier). It was confirmed that the observed I-V and C-V curves were well simulated by this model, thus indicating that the CER effects originated in the field emission current through different SBHs and at different locations of the Schottky junctions. Based on these results, we explain the mechanism of the CER effect qualitatively in terms of this model. For this purpose, we take into account the pinched-off effect caused by the small-scale inhomogeneity of SBH and the existence of deep levels as a result of defects and unintentional impurities in the depletion layer of the $\mathrm{Pt}/\mathrm{Sr}{\mathrm{Ti}}_{1-x}{\mathrm{Nb}}_x{\mathrm{O}}_3$ Schottky junctions.

• Received 24 May 2010

DOI:https://doi.org/10.1103/PhysRevB.83.125317