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  3 HEMT basic

   3.4 HEMT operation

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A high electron mobility transistor (HEMT) is a kind of a field effect transistor where the current flow between two ohmic contacts, source and drain, is controlled by a third contact, the gate which may be a Schottky barrier contact in most cases.⁽¹⁾  Usually a field effect transistors channel is formed by a doped region as is generally the case for well known metal oxid semiconductor field effect transistor - MOSFET. Instead of that, HEMT incorporates a junction between two different semiconductor materials (i.e. a heterojunction) as the channel. The current is controlled in a way, that the transistor channel is normally open without gate biased (Fig. 3.6) .

HEMT advantages:

• High speed
• High gain
• Low noise
• High power density

Fig. 3.6 HEMT operation

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