Wavy transistors deliver ultrahigh definition displays

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Could the future of flexible displays be driven by wavy transistors that vertically gain width without increasing their on-chip footprint?

Researchers at the King Abdullah University of Science and Technology think it could be. They have developed a highly flexible ultrahigh resolution display that could have benefits for next-generation mobile electronics. Using a unique transistor architecture they have been able to boost the performance of the display circuitry.

Flat-panel displays implemented in mobile devices rely on planar transistor circuits to achieve high-resolution and fast imaging. The thin-film transistors, used in these circuits, act as switches and control the electric current that activates individual image elements, or pixels, consisting of light-emitting diodes (LEDs) or liquid crystals.

Future displays are expected to offer an even better visual experience but while transistor miniaturisation can augment resolution, the higher field-effect mobility of the channel material will better address this, according to researchers. It does this through its ability to facilitate electron and hole flows between contacts under applied voltage, which then allows transistors to switch faster and occupy a smaller pixel area.

Amorphous-oxide semiconductors, such as zinc oxide and indium-gallium zinc oxide, have provided transistor channels with modest mobility but scaling down these transistors is both expensive and can introduce flaws known as short-channel effects that tend to increase their power consumption and degrade performance.

According to Muhammad Hussain, who led the research team, an alternative is non-planar vertical semiconductor fin-like structures that are laterally interconnected to form wavy transistor arrays. The researchers opted for zinc oxide as the active channel material and generated the wavy architecture on a silicon substrate before transferring it onto a flexible soft polymer support using a low temperature process.

Due to its vertical orientation, researchers were able to widen the transistors by 70% without expanding their occupied pixel area, doubling the transistor performance.The wavy arrays exhibited reduced short-channel effects and higher turn-on voltage stability compared to their planar equivalents. Moreover, in a proof-of-concept experiment, they were able to drive flexible LEDs at twice the output power of their conventional counterparts.