First GHz Switching Metal Oxide TFT


Ultrafast TFTs made from InGaZnO could be used to make more flexible electronic circuits, say researchers

Scientists as the University of Manchester and Shandong University in China have developed an ultrafast, thin film transistor (TFT) made out of the metal oxide semiconductor InGaZnO. The TFT is claimed to be first oxide-semiconductor based transistor capable of operating at a benchmark speed of 1 GHz. Using such TFTs could help to make next generation screens faster, brighter and more flexible, according to the researchers.

TFTs are mainly used in LCD screens to rapidly switch each individual pixel on and off. Most current TFTs are silicon-based and as such are opaque and rigid in comparison to the oxide semiconductor family of transistors which the team from the UK and China is developing. Whilst oxide TFTs will improve picture quality on LCD displays, it is their flexibility that is even more impressive, says Aimin Song, professor of Nanoelectronics in the School of Electrical & Electronic Engineering, the University of Manchester.

"TVs can already be made extremely thin and bright. Our work may help make TVs more mechanically flexible and even cheaper to produce. But, perhaps even more importantly, our GHz transistors may enable medium or even high performance flexible electronic circuits, such as truly wearable electronics. Wearable electronics requires flexibility and in many cases transparency, too. This would be the perfect application for our research. Plus, there is a trend in developing smart homes, smart hospitals and smart cities - in all of which oxide semiconductor TFTs will play a key role," he explains.

Metal oxide-based semiconductor technology has seen rapid development when compared to its silicon counterpart which is increasingly close to some fundamental limitations. Song says there has been fast progress in oxide-semiconductors in recent years and extensive efforts have been made in order to improve the speed of oxide-semiconductor-based TFTs.

So much so some oxide-based technology has already started replacing amorphous silicon in some gadgets. Song thinks these latest developments have brought commercialisation much closer.

He added: "To commercialise oxide-based electronics there is still a range of research and development that has to be carried out on materials, lithography, device design, testing, and last but not the least, large-area manufacturing. It took many decades for silicon technology to get this far, and oxides are progressing at a much faster pace.

"Making a high performance device, like our GHz IGZO transistor, is challenging because not only do materials need to be optimised, a range of issues regarding device design, fabrication and tests also have to be investigated. In 2015, we were able to demonstrate the fastest flexible diodes using oxide semiconductors, reaching 6.3 GHz, and it is still the world record to date. So we're confident in oxide-semiconductor based technologies. "

'Amorphous-InGaZnO Thin-Film Transistors Operating Beyond 1 GHz Achieved by Optimizing the Channel and Gate Dimensions'; IEEE Transactions on Electron Devices; Volume: 65 Issue: 4

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