SINGLE ELECTRON TUNNELING TRANSISTOR

Contributor : Midhun M.K.

The chief problems that are faced by chip designers are regarding the size of the chip. According to Moore’s Law, the numbers of transistors on a chip will approximately double every 18 to 24 months. Moore\'s Law works largely through shrinking transistors-the circuits that carry electrical signals. By shrinking transistors, designers can squeeze more transistors into a chip. However, more transistors mean more electricity and heat compressed into an even smaller space. Furthermore, smaller chips increase performance but also compound the problem of complexity. To solve this problem, the single-electron tunneling transistor (SET) - a device that exploits the quantum effect of tunneling to control and measure the movement of single electron was devised. Experiments have shown that, charge does not flow continuously in these devices but in a quantized way. This paper discusses the principle of operation of SET, its fabrication and its applications. It also deals with the merits and demerits of SET compared to MOSFET. Although it is unlikely that SETs will replace FETs in conventional electronics, they should prove useful in ultra-low-noise analog applications. Moreover, because it is not affected by the same technological limitations as the FET, the SET can approach closely the quantum limit of sensitivity. It might also be a useful read-out device for a solid-state quantum computer. In future when quantum technology replaces the current computer technology, SET will find immense applications. Single Electron Tunneling transistors (SETs) are three-terminal switching devices that can transfer electrons from source to drain one by one. The structure of SETs is similar to that of FETs. The important difference, however, is that in an SET the channel is separated from source and drain by tunneling junctions, and the role of channel is played by an “island”. The particular advantage of SET is that they require only one electron to toggle between ON and OFF states. So this transistor will generate much less heat and require less power to move the electrons around - a feature very important in battery-powered mobile devices, such as cell phones. We know that the Pentium chips become much too hot and require massive fans to cool them. This wouldn’t\'t happen with a Single Electron Transistor, which uses much less energy, so they can be arranged much closer together.

Reference:

• http://physicsweb.org/articles/world/11/9/7/1
• http://emtech.boulder.nist.gov/div817b/whatwedo/set/set.htm