Backward diodelike behavior in La0.67Ca0.33MnO3−δ∕SrTiO3∕Nb–SrTiO3 p-i-n junction

We report the fabrication of La0.67Ca0.33MnO3−δ∕SrTiO3∕Nb–SrTiO3 p-i-n junction by pulsed laser deposition. This p-i-n junction shows good rectifying property. The most interesting phenomena observed in this p-i-n junction are the backward diodelike behavior above 210K and the transition to the normal diodelike behavior at low temperatures. The backward diodelike behavior, which has not been reported for the manganite based p-n or p-i-n junctions, can be understood by the nearly degenerate model. The coexistence of the ferromagnetic phase and charge ordering phase in the ultrathin La0.67Ca0.33MnO3−δ thin film can account for the behavior of this p-i-n junction at low temperatures. It is also shown that the electric current in this p-i-n junction is dominated by tunneling process at small bias voltages and diffusion process at high bias voltages. This work implies that manganite based diodes can show various properties displayed by the conventional semiconductor diodes.