MOSFET Device Physics and Operation

1 MOSFET Device Physicsand INTRODUCTIONA field effect transistor (FET) operates as a conducting semiconductor channel with twoohmic contacts thesourceand thedrain where the number of charge carriers in thechannel is controlled by a third contact thegate. In the vertical direction, the gate-channel-substrate structure (gate junction)can be regarded as an orthogonal two-terminaldevice, which is either a MOS structure or a reverse-biased rectifying Device that controlsthe mobile charge in the channel by capacitive coupling (field effect). Examples of FETsbased on these principles are metal-oxide-semiconductor FET ( MOSFET ), junction FET(JFET), metal-semiconductor FET (MESFET), and heterostructure FET (HFETs). In allcases, the stationary gate-channel impedanceis very large at normal operating basic FET structure is shown schematically in Figure most important FET is the MOSFET .

operation when the voltage applied between the metal and the semiconductor is more negative than the flat-band voltage (V FB < 0 in Figure 1.3). In the opposite case, when V>V FB, the semiconductor–oxide interface first becomes depleted of holes and we enter the so-called depletion regime. By increasing the applied voltage, the band bending

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