Analysis of carrier modulation in channel of ferroelectric-gate transistors having polar semiconductor

We have been fabricated and characterized a ferroelectric-gate thin-film transistors (TFTs) using ZnO as a channel polar semiconductor and YMnO3 as a ferroelectric gate. A typical n-channel transistor property showing clear drain current saturation in ID–VD (drain current – drain voltage) characteristics was recognized. When the 3 V of the gate voltage is applied under the 4 V of drain voltage, the large drain current of about 1.1 mA is obtained. These controlled-polarization-type ferroelectric-gate TFTs using ZnO-channel TFTs operate in the accumulation–depletion mode and the ON/OFF state of the ferroelectric-gate TFTs strongly depends on the polarization switching of PSFe. In this paper, therefore, the polarization switching of PSFe in the TFT is carefully examined and the relationship between the polarization switching and the carrier accumulation (depletion) state is discussed using impedance spectroscopy and Capacitance–Voltage (C–V) measurements at applied the gate voltage.