Tvärfältstransport

Tvärfältstransport, often abbreviated as TFT, is a phenomenon observed in certain semiconductor devices, particularly in transistors. It refers to the movement of charge carriers, such as electrons or holes, across a channel in response to an electric field applied perpendicular to the direction of current flow. This perpendicular field is typically generated by a gate electrode, which controls the conductivity of the channel beneath it.

In a typical field-effect transistor (FET), such as a MOSFET, the gate voltage modulates the concentration of charge carriers in the channel. When a positive gate voltage is applied to an n-channel MOSFET, it attracts electrons from the source and drain regions to the interface between the semiconductor and the gate insulator. This creates a conductive channel through which current can flow. The electric field from the gate extends into the semiconductor, influencing the charge distribution and thus the conductivity.

The term "tvärfältstransport" specifically highlights the transverse nature of the controlling electric field. While the primary current flows along the channel from source to drain, it is the field applied sideways, across the width of the channel, that dictates the transistor's switching behavior and current amplification. This ability to control current flow with a perpendicular electric field is the fundamental principle behind the operation of most modern transistors. Understanding tvärfältstransport is crucial for designing and analyzing electronic circuits.