1, Politecnico di Milano, Milano, , Italy
The willingness to fabricate transistors capable of high frequency operation is spurred by possible applications like high-resolution flexible displays or devices able to communicate via wireless. This, together with high throughput manufacturing methods such as roll-to-roll coating and inkjet printing, allow organic electronics to be an attractive viable way to make low cost electronics.
So far, a record frequency of transition of 27 MHz is achieved for transistors with lithographic contacts and evaporated semiconductor, while of 20 MHz for transistors fabricated without using masks in the production flow. Nevertheless, the maximum operational frequency of OFETs is going to increase thanks to constant improvements in polymers charge carrier mobility. For such high frequencies, the direct measurement of transistor performances becomes not trivial because of parasitic contributions or the occurrence of resonance.
In this work, a setup for scattering parameter measurement is installed, allowing reliable measurements up to 10 GHz. A process compatible with S-parameters measurement is demonstrated. OFETs are realized through a mask-less approach, combining a fs-laser process for the sintering of high resolution metal electrodes and suitable deposition technique of high mobility polymer semiconductor. For the first time, all-direct-written OFET frequency behavior is characterized using S-parameters, showing transition frequencies falling above the MHz.