Single-Electron Transistor (SET)

A single-electron transistor (SET) is a switching device that consists of two tunnel junctions sharing a common electrode and makes use of this controlled electron tunneling for amplification of current. The technology used in single-electron transistors is based on the theory of quantum tunneling. Considered an important component of nanotechnology, single-electron transistors provide high operating speed and low power consumption.

A single-electron transistor is usually made by keeping two tunnel junctions in series. The transistor consists of a source electrode and a source drain, which is joined with the help of a tunneling island that is also capacitively connected to a gate. The electrons can travel to another electrode only through the insulator. There are two categories of single-electron transistors: metallic and semiconducting. The former makes use of a metallic island, and its electrodes using a shadow mask are mostly evaporated onto an insulator. The latter, in contrast, depends on severing the two-dimensional electron gas that forms at the interface of the semiconductors for the junction.

The resistance feature of a single-electron transistor depends on the size of the nanoparticles, capacitance and electron tunneling.

Single-electron transistors have many applications. They can be used as ultrasensitive microwave detectors and can also be used to detect infrared signals at room temperature. They are also efficient charge sensors capable of reading spin or charge qubits. Their high sensitivity feature allows them to be used as electrometers in experiments requiring high levels of specificity.

Single-electron transistors are not suitable, however, for complex circuits owing to the fluctuations present in them. Other limitations include randomness of the background charge and difficulty in maintaining the room temperature.