Solid State Electronic Devices, 7th Edition

6.3 The Metal–​Semiconductor Fet

The depletion of the channel discussed above for a JFET can be accomplished by the use of a reverse-biased Schottky barrier instead of a p-n junction. The resulting device is called a MESFET, indicating that a metal–​semiconductor junction is used. This device is useful in high-speed digital or microwave circuits, where the simplicity of Schottky barriers allows fabrication to close geometrical tolerances. There are particular speed advantages for MESFET devices in III–​V compounds such as GaAs or InP, which have higher mobilities and carrier drift velocities than Si.

6.3.1 The GaAs MESFET

Figure 6–7 shows schematically a simple MESFET in GaAs. The substrate is undoped or doped with chromium, which has an energy ...