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.