Space-Charge Limited Schottky Diodes with Wide-Bandgap Thin-Film Oxide Heterojunctions

Noncrystalline thin-film Schottky diodes are cost-effective but often exhibit unreliable electrical characteristics due to material imperfections. In this work, a Schottky diode structure is presented utilizing in situ grown Ta₂O₅ and ZnO thin films deposited at room temperature. The low conduction band offset across the interface of the heterogeneous oxides facilitates efficient electron injection under forward bias. Capacitance–voltage characterization reveals a robust Schottky barrier at the Au/Ta₂O₅ interface without a significant barrier thinning effect, enabling high-voltage breakdown up to 65 V and a high on/off ratio of 1 × 10⁸. In demonstrations, the thin-film structure shows Schottky contact characteristics using even a relatively low work function metal of ITO, allowing the operation of transparent Schottky diodes. The diodes show additional potential for applications, including RF-to-DC conversion leveraging space charge capacitance at the Ta₂O₅/ZnO junction and rectifying resistive random access memory devices. This work highlights a promising approach for integrating low-cost, high-reliability Schottky diodes into back-end-of-line processes for wireless electronics and power devices.