MESFET operation principles and device modelling
The MESFET is a three terminal device consisting of two ohmic electrodes named source and drain, and an intermediate control electrode called the gate. In the MESFET case the gate is of the Schottky type that is an intimate contact (without interfacial dielectric) between the metal and a semiconductor (n-type assumed). This type of contact is highly rectifying and, for example, a negative voltage being applied between the gate and the semiconductor bulk, a space charge region exists under the gate which can be controlled by the gate voltage, the associated gate current being very small. This behaviour is quite similar to that of a reverse biased p-n junctions except that the space charge region extends only on one side of the structure (the correct comparison would be with the asymmetrical p+n junction).
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