Nonplanar Design Could Increase Display Flexibility, Resolution and Imaging Speed

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A transistor architecture could boost the performance of display circuitry, leading to flexible ultrahigh-definition displays. The new, nonplanar design uses vertical semiconductor fin-like structures that are laterally interconnected to form wavy transistor arrays. The wavy-shaped thin-film-transistor (TFT) architecture is capable of achieving a 70 percent higher drive current per unit chip area, compared to conventional planar TFT architectures.

Wavy transistor arrays for flexible ultrahigh definition displays, KAUST.
Wavy transistor arrays represent a step toward developing a single gadget with shape and size that can be dynamically reconfigured. Courtesy of Muhammad M. Hussain.

While miniaturization of traditional planar transistor circuits can augment resolution in flat panel displays, researchers surmised that a higher field-effect mobility of the channel material could improve both resolution and frame rate. Specifically, a higher field-effect would facilitate electron and hole flows between contacts under applied voltage, allowing transistors to switch more quickly and occupy a smaller pixel area.

For their transistor design, researchers from King Abdullah University of Science & Technology (KAUST) used zinc oxide as the active channel material and generated the wavy architecture on a silicon substrate. They then transferred it onto a flexible soft polymer support using a low-temperature process.

Due to its atypical architecture, the transistor did not alter the turn-on voltage or the OFF current values, which led to higher performance without compromising static power consumption. The wavy arrays exhibited reduced short-channel effects and higher turn-on voltage stability compared to their planar equivalents.

The architecture’s orientation made it possible for researchers to widen the transistors vertically without expanding the pixel area they occupied. According to the team, this doubled transistor performance. In experiments, the wavy arrays also demonstrated the ability to drive flexible LEDs at twice the output power as their conventional counterparts. The novel architecture was able to drive the LED at 2 times the output power — 3 vs. 1.5 mW— demonstrating its potential use for powering ultrahigh-resolution displays in an efficient manner.

“The LEDs were brighter without increasing power consumption,” said KAUST researcher Muhammad Hussain.

Hussain said that although the trend is toward smaller devices, with reduction in size and weight leading to better displays, most people continue to juggle laptops, tablets and smart phones.

“Having a single gadget with shape and size that can be dynamically reconfigured is a dream we are working toward,” he said, noting that wavy transistor arrays could represent a step toward that goal.

Flexible ultrahigh-resolution displays could be useful for next-generation mobile electronics, such as point-of-care medical diagnostic devices.

The research was published in Small (doi: 10.1002/smll.201703200).

Wavy architecture thin film transistor for ultrahigh-resolution flexible display. Courtesy of KAUST, Muhammad M. Hussain.

Published: January 2018
Research & TechnologyeducationAsia-PacificDisplaysImagingflexible displaysthin film transistorultrahigh resolution displaysTech Pulse

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