A transistor for all purposes

In mobiles, refrigerators, planes – transistors are everywhere. But they often work only in a restricted current range. The LMU physicists have developed an organic transistor that works perfectly under low and high currents.

Transistors are semiconductor devices that control voltage and currents in electrical circuits. To reduce the economic and environmental costs, electronic devices need to become smaller and more efficient. This applies primarily to transistors. In the field of inorganic semiconductors, dimensions smaller than 100 nanometers are already standard. In this regard, organic semiconductors have failed to keep up. In addition, their performance in transport by load is considerably worse. But organic structures offer other benefits. They can easily be printed on an industrial scale, material costs are lower and they can be applied transparently on flexible surfaces.

Thomas Weitz, a professor at the Faculty of Physics of the LMU and a member of the Nanosystems Initiative Munich, and his team are working intensively on the optimization of organic transistors. In their latest publication in Nature Nanotechnology, they describe the manufacture of unusual structure transistors, tiny, powerful and above all versatile. By carefully adapting a small set of parameters during the production process, they were able to design devices at the nanoscale for low or high current densities. The main innovation lies in the use of atypical geometry, which also facilitates the badembly of nanoscopic transistors.

"Our goal was to develop a transistor design that combines the ability to handle high currents typical of conventional transistors with the low voltage operation required for use as an artificial synapse," explains Weitz. Thanks to the successful badembly and characterization of vertical organic field effect transistors with exactly selectable dimensions and ionic tripping, this goal is now achieved.

Potential areas of application for new devices include OLEDs and sensors requiring low voltages, high on-current densities, or high transconductances. Their possible use in so-called memristive elements is of particular interest. "Memristors can be considered as artificial neurons because they can be used to model the behavior of neurons when processing electrical signals," says Weitz. "By accurately adjusting the geometry of a memristive device, it could be applied to various contexts, such as learning processes in artificial synapses." The researchers have already filed a patent application for the device to enable them to develop the new transistor. architecture for industrial use.