High-frequency ZnO schottky diodes for non-contact inductive power transfer in large-area electronics

Besides traditional RFID [1], an emerging application of large-area electronics is hybrid systems [2], where we need to transfer power and signals from one flexible sheet to another. This is driven by manufacturing considerations: sheets providing different functionality, via different materials and devices, can simply be laminated together. Hard-wired metallurgical bonds between flexible sheets are expected to be problematic, especially for reliability, motivating the use of non-contact inductively-coupled interfaces between adjacent sheets [2-3]. For efficiency of such interfaces, high-frequency thin-film diodes (HF-TFDs) are required, since inductive losses are lower at high frequencies [3]. The relevant figure of merit is the cutoff frequency (fc) [4-7], fc=1/(2πRSCD); RS and CD are the series resistance and depletion capacitance. Half wave rectifiers (HWRs) based on nc-Si (fc=110 MHz) [4], IGZO (fc=1.8 GHz, fc=4.2 GHz) [5,6] and ZnO (fc=20 MHz) [7] have been reported. We demonstrate Au/ZnO Schottky diodes with measured fc=700 MHz, and power transfer between adjacent inductors.