Vertical organic transistor technology developed

Physicists of the Technische Universität Dresden have introduced complementary vertical organic transistor technology which is able to operate at low voltage, with adjustable inverter properties, and a fall and rise time demonstrated in inverter and ring oscillator circuits of less than 10 nanoseconds, respectively. With this new technology, described in the journal Nature Electronics, the researchers are just a stone’s throw away from the commercialisation of efficient, flexible and printable electronics of the future.

Poor performance is still impeding the commercialisation of flexible and printable electronics. Hence, the development of low-voltage, high-gain and high-frequency complementary circuits is seen as one of the most important targets of research. High-frequency logic circuits, such as inverter circuits and oscillators with low power consumption and fast response time, are the essential building blocks for large-area, low power-consumption, flexible and printable electronics of the future.

The Organic Devices and Systems (ODS) research group at TU Dresden’s Institute of Applied Physics (IAP), headed by Dr Hans Kleemann, is working on the development of novel organic materials and devices for high performance, flexible and possibly even biocompatible electronics and optoelectronics. Increasing the performance of organic circuits is one of the key challenges in their research. It was only some months ago when PhD student Erjuan Guo announced an important breakthrough with the development of efficient, printable and adjustable vertical organic transistors.

Now, building on their previous findings, the physicists demonstrate for the first time vertical organic transistors (organic permeable base transistors, OPBTs) integrated into functional circuits. Dr Kleemann and his team have succeeded in proving that such devices possess reliable performance, long-term stability and unprecedented performance measures.

“In previous publications, we found that the second control-electrode in the vertical transistor architecture enables a wide range of threshold voltage controllability, which makes such devices become ideal for efficient, fast and complex logic circuits,” said Guo, who has since received a PhD with distinction from TU Dresden.

“In the recent publication, we add a vital feature to the technology by demonstrating complementary circuits such as integrated complementary inverters and ring oscillators,” Guo said. “Using such complementary circuits, the power efficiency and speed of operation can be improved by more than one order of magnitude and might possibly allow organic electronics to enter the GHz regime.”

The complementary inverters and ring oscillators developed at the IAP represent a milestone towards flexible, low-power GHz electronics as it would be needed, for example in wireless communication applications.

“Furthermore, our findings might inspire the entire research community to envision alternative vertical organic transistor designs as they seem to enable high-frequency operation and low cost integrated at the same time,” Guo said.

Image shows a 5-stage complementary ring oscillator composed of organic permeable base transistors.

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