Metal-ferroelectric-semiconductor Field Effect Transistor Research Articles

Film Quality Dependence of Adaptive-Learning Processes in Neurodevices Using Ferroelectric PbZrxTi 1-xO3 (PZT) Films

Partial switching in ferroelectric PbZrx Ti1-x O3 (PZT) thin films has been studied for adaptive-learning metal-ferroelectric-semiconductor field-effect transistor (MFSFET) applications. In particular, the effects of film quality on adaptive-learning processes in ferroelectric PZT thin films are discussed. Dimensionality factor n of the ferroelectric domain growth is estimated to be 1.3-1.4 for sol-gel grown PZT films and 2.0-2.1 for vacuum-evaporated materials. It is shown that this discrepancy results in the difference of the adaptive-learning processes. It is also demonstrated that the learning process in PZT films can gradually proceed by applying the short input pulses.

Modeling of metal-ferroelectric-semiconductor field effect transistor subthreshold current

Abstract A subthreshold current model for metal-ferroelectric-semiconductor field effect transistor (MFSFET) is derived from a new analytical ferroelectric hysteresis model,1.2 the semiconductor surface model,3 the classical diffusion current model,4 as well as the Maxwell equations. The model predicates the shift of MFSFET subthreshold current between forward sweep and backward sweep of gate bias. The simulation results show the effects of coercive voltage, the remanent polarization, the saturation polarization, and the free interface charge between ferroelectric and semiconductor. The external field effect on the saturation polarization (better known as ferroelectric space charge effect) is also modeled. The conventional method to evaluate the interface trapped charge for metal-oxide-semiconductor system is also proposed for MFS system based on the ideal subthreshold current model and its experimental data.

Adaptive-learning neuron circuits using ferroelectric thin films

Abstract Adaptive-learning neuron circuits are reviewed, in which a pulse frequency modulation (PFM) system is used and the interval of output pulses is changed through the learning process. Key devices of the circuits are MFSFETs (Metal Ferroelectric Semiconductor Field Effect Transistors). They are used for representing the synaptic weights of neurons and the polarity of the films is gradually changed by applying input pulses to the gates. In order to produce PFM signals, circuit using a UJT (unijunction transistor) is discussed. As a preliminary experiment for realization of MFSFETs, the electrical properties of metal ferroelectric metal (MFM) capacitor using sol-gel derived PZT films are discussed.

Partial Switching Kinetics of Ferroelectric PbZrxTi1-xO3 Thin Films Prepared by Sol-Gel Technique

Switching characteristics of ferroelectric PbZrx Ti1-x O3 thin films prepared by the sol-gel technique have been studied for “adaptive learning” metal-ferroelectric-semiconductor field effect transistor (MFSFET) applications. It is demonstrated that by applying positive short pulses to the metal-ferroelectric-metal (MFM) capacitors, the polarization of PZT films can be gradually reversed. We have also measured the switching characteristics by applying various input voltages. Experimentally measured current responses and polarization changes can be well fitted by the Kolmogorov-Avrami theory by taking into account the voltage dependence of the reversed polarization.

Characteristics of lithium niobate based capacitors and transistors

Abstract The electrical properties of thin film (<1000 A) capacitor devices of lithium niobate grown on silicon and platinum and of thicker film metal-ferroelectric-semiconductor field effect transistors (MFSFET) with lithium niobate as the gate material were measured. Dielectric constants of the thin films on silicon were as high as 27, while those for films on platinum were as high as 49. The MFSFET structures showed good FET properties, and demonstrated a channel current modulation consistent with switching of the ferroelectric gate by pulsing.