Chemically sensitive field effect transistor

A chemically sensitive field effect transistor (ChemFET for short) is a special form of a field effect transistor that is used as a sensor for chemicals and chemical properties of substances. The structure of a ChemFET essentially corresponds to that of a field effect transistor with insulated gate (IGFET), which also includes the well-known MOSFET , in which the conductive (mostly metallic) gate electrode has been removed and replaced with an aqueous solution . The liquid (there are also ChemFETs for gases) and the substances it contains therefore have direct access to the gate insulating layer and can accumulate there. This can lead to a concentration-dependent development of an electrical potential at the interface, which, analogous to the applied potential in conventional IGFETs, changes the electrical conductivity of the semiconducting channel located under the insulating layer . Depending on the functionalization of the insulator surface, a ChemFET can therefore be used to determine atoms, molecules and ions in liquids and gases, for example as a biosensor in a chip laboratory .

The following subtypes of ChemFETs are known. However, the demarcation between the subtypes is fluid and the terms are sometimes used synonymously:

ion-sensitive field effect transistor (ISFET): the best-known representative of ChemFETs. It is used, for example, to determine ions in electrolytes .
Enzyme field effect transistor (ENFET), a specialized form for the detection of enzymes.
pH sensitive field effect transistor (pHFET)

ChemFETs can also be classified according to the contacted medium

Electrolyte-oxide-semiconductor field-effect transistor (EOSFET)
gas sensitive field effect transistor (GASFET)

Individual evidence

↑ Jürgen Fessmann, Helmut Orth: Applied chemistry and environmental technology for engineers: manual for study and operational practice . Hüthig Jehle Rehm, 2002, ISBN 978-3-609-68352-2 , p. 352-361 .
^ Friedemann Völklein, Thomas Zetterer: Practical knowledge of microsystem technology: Fundamentals - technologies - applications . Vieweg + Teubner, 2006, ISBN 978-3-528-13891-2 , pp. 234-235 .

[1] Jürgen Fessmann, Helmut Orth: Applied chemistry and environmental technology for engineers: manual for study and operational practice . Hüthig Jehle Rehm, 2002, ISBN 978-3-609-68352-2 , p. 352-361 .

[2] Friedemann Völklein, Thomas Zetterer: Practical knowledge of microsystem technology: Fundamentals - technologies - applications . Vieweg + Teubner, 2006, ISBN 978-3-528-13891-2 , pp. 234-235 .