Vertical Organic Thin-Film Transistor with Anodized Permeable Base for Very Low Leakage Current

The Organic Permeable Base Transistor (OPBT) is currently the fastest organic transistor with a transition frequency of 40 MHz. It relies on a thin aluminum base electrode to control the transistor current. This electrode is surrounded by a native oxide layer for passivation, currently created by oxidation in air. However, this process is not reliable and leads to large performance variations between samples, slow production and relatively high leakage currents. Here, we demonstrate for the first time that electrochemical anodization can be conveniently employed for the fabrication of high performance OPBTs with vastly reduced leakage currents and more controlled process parameters. Very large transmission factors of 99.9996% are achieved, while excellent on/off ratios of 5x10$^5$ and high on-currents greater than 300 mA/cm$^2$ show that the C$_{60}$ semiconductor layer can withstand the electrochemical anodization. These results make anodization an intriguing option for innovative organic transistor design.