The transformation of high-frequency vibrations of piezoelectric elements into continuous linear motion of a slider is one of the main tasks of a linear piezoelectric motor. To produce a high thrust force in the piezoelectric linear actuator, we proposed the compound piezoelectric linear actuator based on a ''shaking beam'' excited by two sources of longitudinal mechanical vibrations shifted by =2. The compound actuator consists of two shaking beams and is rigidly fastened. The finite element method (FEM) was used to define structural and electrical boundary conditions for the compound piezoelectric actuator. FEM analysis showed that the compound actuator's trajectory was elliptical. Experimental research has shown that the compound piezoelectric actuator has high thrust force.

In order to overcome the small current drivability of a tunneling field-effect transistor (TFET), we have introduced a TFET with the SiGe body and elevated Si drain region. The proposed TFET features large on-current and lower subthreshold swing (SS) compared with the Si TFET. Also, by using elevated Si drain region, it is expected that ambipolar current can be suppressed. Through the technology computer aided design (TCAD) simulation, the characteristics of the proposed TFET have been investigated to confirm its superiority in performance. The proposed TFET structure enables self-aligned doping process and has a strong immunity to short-channel effects compared with the conventional TFET. In addition, we have confirmed that both n-and p-channel characteristics can be simultaneously improved by using the proposed TFET.

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In this work, electrical characteristics of L-shaped tunneling field-effect transistors (TFETs) have been studied and optimized by a commercial device simulator: Synopsys Sentaurus. Unlike our previous study performed by using Silvaco Atlas, there exists a kink phenomenon in a transfer curve which degrades the subthreshold swing (SS) and on-current (lon) of TFETs. According to simulation results, the kink results from abrupt source doping. Rounding the source junction edge with gradual doping profile is helpful to alleviate it. Based on those results, a novel fabrication flow has been proposed to suppress the kink effect induced by source corners. It is predicted that the performance of L-shaped TFETs is improved in terms of SS and Ion under the optimized process condition. Furthremore, the effect of high-k gate dielectric and narrow band gap material on device performance has been examined. Using 2-nm-thick HfO2 for gate dielectric and Si0.7Ge0.3 for intrinsic tunneling region, gate controllability to the channel and tunneling probability have been enhanced. As a result, its threshold voltage (Vth), SS and Ion have been improved by 0.13 V, 16 mV/dec, and 3.62 microA/microm, respectively.

Abstract-In this work, a tunneling field-effect transistor (TFET) based on heterojunctions of compound and Group IV semiconductors is introduced and simulated. TFETs based on either silicon or compound semiconductors have been intensively researched due to their merits of robustness against short channel effects (SCEs) and excellent subthreshold swing (SS) characteristics. However, silicon TFETs have the drawback of low on-current and compound ones are difficult to integrate with silicon CMOS circuits. In order to combine the high tunneling efficiency of narrow bandgap material TFETs and the high mobility of III-V TFETs, a Type-I heterojunction tunneling fieldeffect transistor (I-HTFET) adopting Ge-Al x Ga 1-x AsGe system has been optimized by simulation in terms of aluminum (Al) composition. To maximize device performance, we considered a nanowire structure, and it was shown that high performance (HP) logic technology can be achieved by the proposed device. The optimum Al composition turned out to be around 20% (x=0.2).Index Terms-Tunneling field-effect transistor (TFET), Type-I heterojunction, narrow bandgap material, high mobility, simulation, nanowire, high performance (HP) logic technology

Abstract-In this work, a novel silicon (Si) based floating body synaptic transistor (SFST) is studied to mimic the transition from short-term memory to long-term one in the biological system. The structure of the proposed SFST is based on an n-type metaloxide-semiconductor field-effect transistor (MOSFET) with floating body and charge storage layer which provide the functions of short-and long-term memories, respectively. It has very similar characteristics with those of the biological memory system in the sense that the transition between shortand long-term memories is performed by the repetitive learning. Spike timing-dependent plasticity (STDP) characteristics are closely investigated for the SFST device. It has been found from the simulation results that the connectivity between pre-and postsynaptic neurons has strong dependence on the relative spike timing among electrical signals. In addition, the neuromorphic system having direct connection between the SFST devices and neuron circuits are designed.Index Terms-Neuromorphic system, synaptic transistor, short-and long-term memory, spike timing-dependent plasticity (STDP)

In order to improve the internal quantum efficiency of GaN-based LEDs, a LED structure featuring a p-type trench in the multi-quantum well (MQW) is proposed. This structure has effects on spreading holes into the MQW and reducing the quantum-confined stark effect (QCSE). In addition, two simple fabrication methods using electron-beam (e-beam) lithography or selective wet etching for manufacturing the p-type structure are also proposed. From the measurement results of the manufactured GaN-based LEDs, it is confirmed that the proposed structure using e-beam lithography or selective wet etching shows improved light output power compared to the conventional structure because of more uniform hole distribution. It is also confirmed that the proposed structure formed by e-beam lithography has a significant effect on strain relaxation and reduction in the QCSE from the electro-luminescence measurement.

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