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How does a positive gate voltage turn on an n-channel MOSFET?

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NMOS transistorNegative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors. — transistor NMOS transistor
Negative-channel metal-oxide semiconductors (NMOS) employ a positive secondary voltage to switch a shallow layer of p-type semiconductor material below the gate into n-type. For positive-channel metal-oxide semiconductors (PMOS), all these polarities are reversed. NMOS transistors are more expensive, but faster, than PMOS transistors.

In an n-channel metal-oxide-semiconductor field-effect transistor (MOSFET), the device is typically in an "off" state when no voltage is applied to the gate, as the source and drain are separated by a p-type region that prevents current flow.12

When a positive voltage is applied to the gate, it creates an electric field that penetrates the silicon dioxide insulating layer. This positive potential repels the holes (the majority carriers in the p-type substrate) and attracts electrons toward the semiconductor surface directly beneath the gate.12

This accumulation of electrons forms a thin, conductive n-type layer known as the channel. This channel effectively bridges the n+ source and n+ drain regions, creating a continuous path that allows current to flow between them when a voltage is applied across the drain and source. By varying the gate voltage, the conductance of this channel can be modulated, thereby controlling the current through the device.12