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.
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.
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