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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.

The terminals in FET are called Gate, Drain and Source, as opposed to the terminology used for BJTs: Base, Collector and Emitter.

1 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 barrierA Schottky barrier is a metal- semiconductor junction which has rectifying characteristics, suitable for use as a diode. The largest differences between a Schottky barrier and a p-n junction are its typically lower junction voltage, and decreased (almost
• In the HEMTHEMT stands for High Electron Mobility Transistor . A HEMT is a Field effect transistor with a junction between two materials with different band gaps (i. a heterojunction) as the channel instead of an n-doped region. A commonly used combination is GaAs w (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 siliconAmorphous silicon (a-Si) is the non-crystalline form of silicon. Silicon is normally tetrahedrally bonded to four neighboring silicon atoms. This is also the case in amorphous silicon, however, it does not form a continuous crystalline lattice as in cryst or polycrystalline siliconPolycrystalline silicon or polysilicon or poly-Si is a material consisting of multiple small silicon crystals, and has long been used as the conducting gate material in MOSFET and CMOS processing technologies. For these technologies it is deposited using as channel.

2 External links

• PBS The Field Effect Transistor