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Field effect transistor

The Field-Effect Transistor (FET) is a family of transistors that rely on an electric field to control the conductivity of a "channel" in a semiconductor material. FETs, like all transistors, can be thought of as voltage-controlled resistors. Most FETs are made using conventional bulk semiconductor processing techniques, using the single-crystal semiconductor wafer as the active region, or channel. The channel region of TFTs (thin-film transistors), on the other hand, is a thin film that is deposited onto a substrate (often glass, since the primary application of TFTs is in liquid crystal displays). For more on TFTs, see thin-film transistor; the remainder of this article deals with the transistors most commonly used in integrated circuits. In biology, voltage-gated ion channel s work in a similar way.

Types of field-effect transistors

The different types of field-effect transistors can be distinguished by the method of isolation between channel and gate:

  • The MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) utilizes an isolator (typically SiO2).
  • The JFET (Junction Field-Effect Transistor) uses a p-n junction.
  • The MESFET (Metal-Semiconductor Field Effect Transistor) uses a Schottky barrier
  • In the HEMT (High Electron Mobility Transistor), also named HFET (heterostructure FET), the fully depleted wide-band-gap material forms the isolation.


The distinguishing feature of the TFT (Thin-film transistor) is the use of amorphous silicon or polycrystalline silicon as channel.

External Link

PBS The Field Effect Transistor



Last updated: 10-24-2004 05:10:45