Temperature-dependent polarity reversal in $\mathrm{Au}∕\mathrm{Nb}:\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ Schottky junctions

We have observed temperature-dependent reversal of the rectifying polarity in $\mathrm{Au}∕\mathrm{Nb}:\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ Schottky junctions. By simulating current-voltage characteristics, we have found that the permittivity of $\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ near the interface exhibits temperature dependence opposite to that observed in the bulk, significantly reducing the barrier width. At low temperature, tunneling current dominates the junction transport due both to such barrier narrowing and to suppressed thermal excitations. The present results demonstrate that junction properties can be dominated by the interface permittivity.

Figure 1

(Color online) (a) $I\text{−}V$ and (b) $C\text{−}V$ characteristics of a $\mathrm{Au}∕\mathrm{Nb}:\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ Schottky junction at various temperatures: $10\mathrm{K}$ (bold curve), $50\mathrm{K}$ (bold dashed curve), $100\mathrm{K}$ (thin curve), $150\mathrm{K}$ (bold dot-dashed curve), $200\mathrm{K}$ (thin dashed curve), and $300\mathrm{K}$ (thin dot-dashed curve). The junction area is $\sim 0.002{\mathrm{cm}}^2$.

Figure 2

(Color online) (a) $I\text{−}V$ characteristics on a semilogarithmic scale between 300 and $10\mathrm{K}$. Bold, dashed, and dot-dashed curves correspond to the data at 10, 25, and $50\mathrm{K}$, respectively. Higher temperature data are shown by thin curves. Linear fitting is shown by the bold lines. (b) $\ln [J_S\cosh (E_{00}∕kT)∕T]-1∕E_0$ plotted between 300 and $10\mathrm{K}$ (dots connected with a dashed line). The bold line is a linear fit for the temperature region between 300 and $100\mathrm{K}$.

Figure 3

(Color online) Schematic potential profiles of the $\mathrm{Au}∕\mathrm{Nb}:\mathrm{Sr}\mathrm{Ti}{\mathrm{O}}_3$ Schottky junction under the (a) reverse-bias condition and (b) forward-bias condition. The thick and thin arrows show the direct and thermally assisted tunneling processes, respectively.

Figure 4

(Color online) (a) Simulated temperature dependence of the relative permittivity in the depletion region, (b) barrier potential profile, and (c) $I\text{−}V$ characteristics calculated for a barrier height of $1.41\mathrm{V}$ and a donor concentration of $5\times {10}^{19}{\mathrm{cm}}^{-3}$. The results at 300, 200, 100, and $10\mathrm{K}$ are shown by dot-dashed, dashed, thin, and bold curves, respectively.