  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.
