Electrical Characteristics of Controlled-Polarization-Type Ferroelectric-Gate Field-Effect Transistor

We propose a novel ferroelectric-gate field-effect transistor (FET) with a polar semiconductor channel, which is called a controlled-polarization-type ferroelectric-gate FET. The essential factor for this device is the stabilization of the spontaneous polarization of the ferroelectric film by the spontaneous polarization of a polar semiconductor, such as ZnO or GaN. We demonstrate two types of controlled-polarization-type ferroelectric-gate thin film transistors (TFTs), which are the ZnO/YMnO 3 /Pt bottom-gate-type structure and Pt/PZT/ZnO top-gate-type structure. Both structures show n-channel-type transistor operation with the memory effect originating from ferroelectricity. From the electrical characteristics of ferroelectric-gate TFTs, the effects of ferroelectricity, gate leakage current, space charge, and charge injection on the device operation are discussed.