An illustration of the dual-gated device developed by IISc Bengaluru scientists. Image: IISc BengaluruThrough time transistors — the building blocks of electronic devices – have become smaller by the day, making apparatus quicker and compact. A group of Indian scientists have discovered a means to address this dilemma.

An illustration of the dual-gated device developed by IISc Bengaluru scientists.

Transistors work by behaving like digital switches controlling the flow of current across circuits. The most typical kind of transistors called MOSFETs (metal–oxide–semiconductor field-effect transistors) can’t switch from ‘on’ to ‘away’ unexpectedly and thus flow present even after the unit is turned off. The bigger the transistors are more power they waste. Tunnel FETs (field-effect transistors) squander less electricity but are more suited for low-performance devices such as watches or laptop computers.

Scientists at the Indian Institute of Science (IISc) in Bengaluru have united these two different types of transistors into a single device that can easily change between power-efficient and high-performance modes, based on the requirement. The apparatus has a distinctive sort of metal-semiconductor junction that may be tweaked to make it behave either like a MOSFET or even a tube FET.

When the gate is in the OFF position, there’s a large energy barrier that prevents electrons from crossing over. After the gate is turned on with voltage, the height of this barrier is decreased and electrons could jump over. The smaller the distribution voltage to turn the transistor on, more efficient is that the apparatus,” explained Dr. Navakanta Bhat, head of the Centre for Nano Science and Engineering at IISc who headed the research group.

However, he said, bringing down supply voltage for MOSFETs proportionately with transistor size is tough because of a fundamental design flaw. A variable called subthreshold swing — that determines the minimal gate voltage necessary for the transistor to switch from on to off — restricts the distribution voltage to be not less than 1 volt.

To overcome this, scientists have tried using tunnel FETs in which instead of the height, the diameter of the electron barrier is reduced to a stage where electrons are in a position to “tunnel” through instead of leaping over it.

In the current work, researchers made a hybrid apparatus capable of switching between MOSFET and tube FET modes using two gates rather than a single, and a distinctive kind of electron barrier generated by joining a metallic and semiconductor under certain conditions. The dual-gated device, Dr. Bhat said, can operate at a voltage lower than possible with conventional MOSFETs, significantly reducing electricity consumption.

The study results are published in journal Applied Physics Letters. The team included Dr. Bhat and Shubhadeep Bhattacharjee.


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