Cambridge engineers have developed ultra-low-power IGZO transistors

Researchers from the University of Cambridge have developed a new transistor made of thin films of indium oxide, gallium and zinc , which is powered by the external environment. The unique design of the transistor will allow devices to function without a battery for several months or even years. This technology opens up broad prospects for the development of wearable or implantable electronics. Scientists presented the results of their work in the journal Science on October 21, 2016.

“This will lead to a new design model for ultra-powerful sensors of sensor interfaces and analog signal processing in wearable and implantable devices. All of them are critically important for the Internet of Things, ”said Arokia Natan, a professor at the Technical Sciences Department, one of the authors of the study.

Indium, gallium and zinc oxide (IGZO), which comprises the new development of Cambridge engineers, is a semiconductor material that is used to create thin-film transistors. Since 2012, such transistors have been used in some flat panel displays, smartphones and tablets. Until now, IGZO transistors have not been launched into mass production due to expensive equipment and a fairly long process of creating a single sample. It is possible that the technology that was used to create the "Cambridge" sample, will require less cost.
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IGZO-transistors work on the principle of a computer in sleep mode. The new transistor is fed by the smallest leakage currents near the off state. This leakage at the point of contact between the metal and semiconductor components of the transistor, the so-called " Schottky barrier, " is an undesirable characteristic. This small “portion” of current is comparable to how water drips from a faulty tap, and is common to all transistors. Scientists for the first time managed to turn this drawback into favor and use it functionally. This feature of the new transistors opens up new possibilities for designing the IoT system.


“We challenged the generally accepted understanding of what a transistor should be,” says Professor Nathan. “We found that the Schottky barrier, which most engineers try to avoid, actually have ideal characteristics for wearable or implantable electronics of interest for monitoring health status.”

Transistors can be manufactured at low temperatures and printed on virtually any material: from glass and plastic to fabric and paper. The new design half solves one of the main problems that impede the development of transistors of ultralow power, namely the ability to produce them in very small sizes. As the transistors become smaller, their two electrodes begin to influence each other's behavior, which means that smaller than a certain size transistors will not work as desired. By changing the design of the transistor, Cambridge researchers were able to use the Schottky barriers so that the electrodes remained independent of each other. Therefore, in the near future it will be possible to produce transistors of very small size.

“This is an original transistor design. This type of ultra-low-power supply is a prerequisite for the development of various types of new devices, where function, in essence, “intelligence”, and not speed, is important. Fully autonomous electronics in such devices is becoming more real today. They can work on the background energy received from the environment, which will increase their lifespan, ”said Gehan Amaratunga, a professor at the development department.

The design of the transistor allows you to enhance the signal. The operating voltage of the transistor is less than a volt, with energy consumption below one billionth of a watt. This ultra low power consumption makes them most suitable for applications where functionality and durability are more important than speed. That, in fact, lies in the idea of ​​the Internet of things.

“If we were to draw energy from conventional AA batteries based on this design, it could work for a billion years,” said Dr. Sonsik Lee, lead author of the study. “The use of the Schottky barrier does not allow the electrodes to interfere with each other in order to amplify the amplitude of the signal even in the state when the transistor is almost turned off.”

Russian science is trying to keep up in the race for the creation of ultra-low-power transistor. Half a year ago, Russian engineers together with colleagues from Japan presented the concept of a graphene transistor. Its design is based on the use of double-layer graphene. According to the researchers, the transistor of this material can operate at low voltage (0.5 volts) and at high frequencies (up to 100 GHz). Such conclusions were made on the basis of calculations — so far only the device model has been developed.


In addition to working on components for IoT devices, researchers at Cambridge University are paying attention to the development of implantable electronics. Two years ago, they developed artificial muscles that can imitate natural contractions. They are made of polymers that can change their size and shape under the influence of an electrical signal. With the help of a number of mechanisms and physiological stimuli, movements close to natural can be reproduced in artificial material.