Dynamics of Charge Flow in the Channel of a Thin-Film Field-Effect Transistor

TL;DR

This paper analyzes how charge flow dynamics in thin-film FET channels depend on frequency and position, providing a method to determine charge mobility from electro-optic measurements.

Contribution

It introduces an approximate expression for the frequency dependence of induced charge, aiding in charge mobility determination in thin-film FETs.

Findings

Derived an expression for charge frequency dependence in the channel center.

Validated the model with electro-optic measurements on organic transistors.

Provided a practical approach for mobility estimation in thin-film FETs.

Abstract

The local conductivity in the channel of a thin-film field-effect transistor is proportional to the charge density induced by the local gate voltage. We show how this determines the frequency- and position-dependence of the charge induced in the channel for the case of "zero applied current": zero drain-source voltage with charge induced by a square-wave voltage applied to the gate, assuming constant mobility and negligible contact impedances. An approximate expression for the frequency dependence of the induced charge in the center of the channel can be conveniently used to determine the charge mobility. Fits of electro-optic measurements of the induced charge in organic transistors are used as examples.