Silicon Single Electron Transistor

Silicon Single Electron Transistor

Single electron transistor (SET) is an important discovery in microelectronics science. Due to the ability to control the tunneling process of a single electron in a micro tunnel junction system, multiple functional devices can be designed using it. In modern submicron devices, the limiting factor for device operation speed is during capacitor charging and discharging The capacitance of a single electron transistor is only about 10-16F, and it can achieve a specific function by controlling a single electron, so its response speed and power consumption are thousands of times better than the limit data of traditional transistors. PAM-XIAMEN can supply Silicon wafer for single electron transistor fabrication to study quantum tunneling transport, take the following specification for example:

Single Electron Transistor Wafer

1. Silicon Wafer Specification for SET Fabrication

Silicon Wafer: 76.2mm P(100) 1-10 ohm-cm SSP 380um with 1 micron of Thermal Oxide

More silicon specifications please refer to

A brief introduction to the fabrication process of silicon single electron transistor by STM anodic nanooxidation processing is as follows(shown as Fig.1):

1) Precipitate a certain thick Ti on Si/SiO2 substrates;

2) Using an STM probe as the cathode, nano sized titanium oxide wires are formed by adsorbing water in the air on the surface of Ti;

3) Form source and drain electrodes;

4) Manufacturing gates.

Diagram of Silicon SET Fabrication by STM Anodic Nanooxidation Processing

Fig.1 Diagram of Silicon SET Fabrication by STM Anodic Nanooxidation Processing

2. About Single Electron Transistor

2.1 Single Electron Transistor Properties

SET shares many similarities with MOSFET and Coulomb systems:

Structurally, the naming of each component borrowed the names of MOSFET and Coulomb blocking systems;

The working form controls the source and leakage currents by applying a certain voltage to the gate.

SET replaces the channel of MOSFET with tunnel barrier Coulomb island tunnel barrier, so the working mechanism is completely different. SET is actually a gate controlled Coulomb blocking system based on Coulomb blocking effect and quantum size effect.

2.2 How does A Single Electron Transistor Work?

The working of single electron transistor can be illustrated in terms of Coulomb Blockage and Quantum Tunneling, specifically as:

Coulomb blockage effect: one of the extremely important physical phenomena observed in solid-state physics in the 1980s. When the size of a physical system reaches the nanometer level, the charging and discharging processes of the system are discontinuous, that is to say, quantized. At this point, the energy E required to charge an electron is e2/2C, where e is the charge of an electron and c is the capacitance of the physical system. The smaller the system, the smaller the capacitance c, and the larger the energy E. We call this energy Coulomb blocking energy, which is the Coulomb repulsion energy of the preceding electron to the following electron when entering or leaving the system. So, for the charging and discharging process of a nanosystem, electrons cannot be continuously transported collectively, but rather through individual electron transfers. The specificity of individual electron transport in nanosystems is commonly referred to as Coulomb blockade effect.

Quantum tunneling: if two quantum dots are connected through a tunnel junction, the process of a single electron passing through a potential barrier from one quantum dot to another is called quantum tunneling. In order for a single electron to tunnel from one quantum dot to another, its energy (ey) must overcome the Coulomb blocking energy E of the electron, i.e. V>e/2C, where C is the capacitance of the tunnel junction between two quantum dots. Coulomb blockade and quantum tunneling are both observed at extremely low temperatures.

3. Si based Single Electron Transistor Applications

The most promising application of single electron transistor is to replace MOS devices as the basic unit for constructing large-scale integrated circuits when the size of MOS devices reaches its limit. The earliest application of SET may be in the field of memory. It also can be used as super sensitive ammeters, near-infrared radiation receivers, and DC current standards.

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