Impedance Analysis of Controlled-Polarization-Type Ferroelectric-Gate Thin Film Transistor Using Resistor--Capacitor Lumped Constant Circuit

概要

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We propose a novel ferroelectric-gate field-effect transistor using a polar oxide semiconductor channel, which is called a controlled-polarization (CP)-type ferroelectric-gate thin film transistor (TFT). Although the CP-type ferroelectric-gate TFTs with a ZnO/YMnO3 structure shows nonvolatile memory operation, the relationship between the electrical characteristics of the TFTs and the direction of spontaneous polarization of the ferroelectric layer ($P_{\text{SFe}}$) below the channel has not been revealed. In this study, the direction of $P_{\text{SFe}}$ is analyzed by the impedance spectra of the channel conductance because it can be expected that the channel conductance depends on the direction of the $P_{\text{SFe}}$. The five conditions of the channel conductance are assumed and the impedances between the source electrode and the gate electrode of each condition are calculated by SPICE. The direction of $P_{\text{SFe}}$ at various gate voltages is determined by the comparison of the calculated results and experimental results. It was found that the channel conductance of the ferroelectric-gate TFT has steep change by the change of the direction of $P_{\text{SFe}}$.
2011-04-25