The world's first junctionless nanowire transistor

A team of scientists at the Tyndall National Institute, Ireland, have designed and fabricated the world s first junctionless transistor that could revolutionise microchip manufacturing in the semiconductor industry. Prof. Jean-Pierre Colinge's breakthrough on the microchip transistor was published recently in Nature Nanotechnology journal.

The transistor is the fundamental building block in all electronic devices. Since the early seventies the number of transistors in a silicon chip has grown from a few hundred to over two billion transistors on a single chip today. The exponential increase in demand for feature packed electronic devices is driving the semiconductor industry to produce chips that need to be smaller, more energy efficient and more cost effective than ever before. As a consequence transistors are becoming so small that conventional transistor architectures, used since the seventies, can no longer be used.

Current technologies require fabrication processes that are both complex and costly. All existing transistors are based on junctions. A junction is formed when two pieces of silicon with different polarities are placed side by side. Controlling the junction allows the current in the device to be turned on and off and it is the precise fabrication of this junction that determines the characteristics and quality of the transistor and is a major factor in the cost of production. Tyndall National Institute’s junctionless transistor doesn’t require a junction. "The current flows in a very thin silicon wire and the flow of current is perfectly controlled by a `wedding ring` structure that electrically squeezes the silicon wire in the same way that you might stop the flow of water in a hose by squeezing it. These structures are easy to fabricate even on a miniature scale which leads to the major breakthrough in potential cost reduction," explained Professor Colinge.

The junctionless transistor resembles in a way the first ideal transistor structure, proposed in 1925. But to-date, no-one had been able to fabricate it. He attributed the successful fabrication at Tyndall to the skill and expertise of researchers who were able to fabricate silicon nanowire with a diameter of a few dozen atoms using electron-beam writing techniques and expertise available at Tyndall.