Chemical field-effect transistor

A chemically sensitive field effect transistor (abbreviated ChemFET ) is a special form of a field effect transistor, which is used as a sensor for chemical and chemical properties of substances. Building a ChemFETs substantially corresponds to that of a field effect insulated gate transistor ( IGFET ), which also includes the known MOSFET is one in which the conductive (usually metal ) gate electrode has been removed and replaced by an aqueous solution. The liquid (there is also ChemFETs for gases ) and the substances contained in it have therefore direct access to the gate insulating layer and can be deposited there. This may lead to a concentration-dependent configurations of an electric potential at the interface that changes in analogy with the applied potential in conventional IGFETs, the electrical conductivity of the insulating layer located below the semiconductor channel. Depending on the functionalization of the surface may be an insulator ChemFET therefore be used to identify atoms, molecules and ions in liquids and gases, for example, as a biosensor chip in a laboratory.

The following sub- types of ChemFETs are known. However, the distinction between the subtypes are blurred and the terms are sometimes used interchangeably:

• Ion-sensitive field effect transistor ( ISFET): the most famous representatives of the ChemFETs. It is used for example to identify ions in the electrolyte.
• Enzyme field-effect transistor ( ENFET ), a specialized form for the detection of enzymes.

Also you can ChemFETs divided in terms of the contacted medium

• Electrolyte -Oxide- Semiconductor Field - Effect Transistor ( EOSFET )
• Gas- sensitive field effect transistor ( GASFET )