Showing papers presented at "International Meeting for Future of Electron Devices, Kansai in 2017"

Study on underwater wireless power transfer via electric coupling with a submerged electrode

Abstract: Wireless power transfer (WPT) is studied for battery charging in the IoT world. WPT via electric coupling is studied for apparatuses in water using the effect of large dielectric constant of water. One electrode is isolated from water and another electrode is exposed in water for underwater WPT. The power transfer efficiency is over 75%.

Heteroepitaxial growth of ε-Ga 2 O 3 thin films on cubic (111) GGG substrates by mist chemical vapor deposition

Abstract: We demonstrated that heteroepitaxial e-Ga 2 O 3 thin films can be grown on (111) GGG substrates by mist CVD. The out-of-plane and in-plane epitaxial relationship between the e-Ga 2 O 3 thin film and the (111) GGG substrate was determined to be (0001) e-Ga 2 O 3 [10-10] // (111) GGG [-1-12] by XRD 2θ-ω and φ scanning. This is the first report on heteroepitaxial growth of e-Ga 2 O 3 thin films on (111) GGG substrates by mist CVD.

Reduced current collapse in multi-fingered AlGaN/GaN MOS-HEMTs with dual field plate

Abstract: This paper describes suppression of current collapse by field-plate (FP) in AlGaN/GaN MOS-HEMTs. Current collapse reduction was confirmed for a multi-gate fingered MOS-HEMT with a total gate width of 10 mm. Moreover, we have fabricated a 5-A class MOS-HEMT with both gate-FP and source-FP (dual-FP), showing more complete suppression in current collapse as compared to that with only gate-FP.

A novel SAW resonator with Incredible High-Performances

Abstract: High Q and low TCF are elemental characteristics for SAW resonator, in order to realize high performance filters and duplexers for new LTE frequency bands. Authors have focused on the acoustic energy confinement in vicinity of substrate surface. A novel multi-layered structure substrate have realized incredibly high performances such as Q factor of 4000 and TCF of 8 ppm/°C compared with conventional structure.

Effects of He plasma treatment on zinc oxide thin film transistors

Abstract: We report on the effects of He plasma treatment for reducing contact resistances of ZnO thin-film transistors (TFTs). A TFT with Ti (20 nm)/Au (40 nm) ohmic contacts was fabricated by exposing the ohmic contact area to He plasma before the formation of the Ti/Au ohmic contacts. Schottky like behavior was turned into ohmic behavior by the He plasma treatment, indicating the effectiveness of the treatment for reducing the contact resistance for ZnO TFTs. Interestingly, the sheet resistance of the ZnO channel layer decreased from 53.8 GΩ/sq to 6.41 GΩ/sq although the channel portion of ZnO was not treated by the He plasma. The transconductance for a 20-µm-gate TFT was also improved from 4.6 × 10−6 S/mm to 1.2 × 10−4 S/mm.

MEMS mirrors for automotive applications

Abstract: Microelectromechanical system devices are widely employed in automotive electronics because of its low cost, small size and high functionality. Cars are going to be equipped with optical components, especially micromirrors to realize intelligent safety, driving and communication systems. The mechanical reliability of the micromirrors should be addressed, which is discussed in this manuscript.

Characteristic evaluation of Ga-Sn-O films deposited using mist chemical vapor deposition

Abstract: We have evaluated optical and electrical characteristics of Ga-Sn-O (GTO) films deposited using mist chemical vapor deposition (CVD). It was found that the GTO film is transparent, which suggests the energy gap is wide. The X-ray diffraction (XRD) indicated that the GTO film was crystallized, but the crystal structure is not clarified now. It was also found that the sheet resistance decreases as the dilution gas flow increases.

An 800-MHz 8-bit high speed SAR ADC in 16nm FinFET process

Abstract: In this paper, we fabricated an 8-bit SAR ADC with a 16-nm FinFET process. A time-interleaved (TI-) ADC is remarked as an ADC with high speed sampling rate. Considering the area, the power consumption and the complexity of the mismatch calibration, it is possible that a unit SAR ADC of the TI-ADC with higher sampling rate improves these performances. We configure the SAR ADC with the high speed operation which is suitable for the advanced CMOS process and describe with the 16-nm FinFET process. Our SAR ADC achieves the 6.53 bits of ENOB with 800 MS/s. We compare other results with other process, and confirm that this SAR ADC can adapt to the advanced CMOS process.

Junction-barrier Schottky diodes fabricated with very thin highly Mg-doped p + -GaN(20 nm)/n-GaN layers grown on GaN substrates

Abstract: Low turn-on voltage junction barrier Schottky (JBS) diodes were fabricated using very thin (20 nm) and extremely highly Mg doped (2×1020 cm−3) p+-GaN layer placed on top of n−-GaN epitaxial layers grown on n-GaN substrates. By omitting p-GaN layers in conventional p+-GaN/p-GaN/n−-GaN vertical p-n junction diodes, device processing has been eased and low specific on-resistances (R on <0.3 mΩcm2) have been obtained.

Silicon-based micro thermoelectric generator fabricated by CMOS compatible process

Abstract: Energy harvester is a key device for realizing trillion sensors network society. Thermoelectric generator (TEG) is regarded as the ultimate energy harvester to provide semipermanent power from heat energies via Seebeck effect. The recent discovery of the superior thermoelectric (TE) property of silicon nanowires (Si-NWs) opens the way for Si-based TEGs. In this paper, a very simple device architecture of Si-based micro TEG is proposed. It can be fabricated by the CMOS-compatible process, and the TE power density is found to be scalable by miniaturizing and integrating the structure.

Creation and study of memristors based on CuCl 2

Abstract: This article describes a method of creating crossbar structures based on copper chloride and results of research such structures. It is shown that the obtained elements have a memristor properties. The used compound can provide better operation speed of elements in comparison with the materials studied earlier. The switching voltages of the investigated structures were 0.2 V and −0.25 V. Measured values of the number of switching and stability characteristics show that memristors can compete with modern silicon devices in the field of computer memory.

Evaluation of PLFSR PUF with several implementation methods for FPGA

Abstract: Physical Unclonable Function (PUF) has been attracted attention as a countermeasure of an imitation of semiconductor. Pseudo linear feedback shift register PUF (PLFSR PUF) is one of the most popular PUFs. However, a performance evaluation of PLFSR PUF due to the difference of implementation has not been reported. Therefore, this study evaluates the performance of PLFSR PUF with several implementation methods.

Physical mechanisms of short-channel effects of lateral double-gate tunnel FET

Abstract: This paper discusses the mechanisms that may underlie the short-channel effects of the lateral double-gate tunnel FET. Simulations suggest that the short-channel effect of the threshold voltage is triggered by degradation in the electrostatic integrity of the gate field.

Protonation-induced change on optical, electrical, and structural properties of epitaxial WO 3 films

Abstract: Protonation and deprotonation processes of c-axis oriented monoclinic WO 3 epitaxial films were studied by fabricating a solution-gate device operated in H 2 SO 4 aqueous solution. The protonation process by positive gate biasing brought about an optical transmittance decrease in visible (VIS) and near-infrared (NIR) regions. The deprotonation process by negative gate biasing recovered the decrease in VIS region while that in NIR one remained. The decrease in NIR region was stable at room temperature in air over several weeks. By analyzing the data on X-ray diffraction and Hall effect measurements, the decrease in VIS region was related to the formation of tetragonal H x WO 3 tungsten bronze and that in NIR region was related to the formation of orthorhombic WO 3 ·0.33H 2 O tungsten hydrate.

Characterization of lightly-doped n- and p-type homoepitaxial GaN on free-standing substrates

Abstract: Hall-effect measurements for n-type and p-type GaN with low doping concentration are presented. The GaN layers were grown by metal-organic vapor phase epitaxy on hydride-vapor-phase-epitaxy-grown free-standing GaN substrates. For n-GaN, the origin of acceptor which compensating donor is not only C but also native defects for the Si doping concentration of 1016 cm−3 level. The electron mobility is mainly limited by ionized impurity scattering or polar optical phonon scattering in the temperature less or higher than 200 K, respectively. For p-GaN, lightly Mg doping of mid 1016 cm−3 was achieved, which shows the donor concentration of 3.2×1016 cm−3 and the mobility of 31 cm2/Vs at 300 K.

Recent topics of vertical GaN power devices

Abstract: In this paper, recent topics of vertical GaN power devices fabricated on GaN substrates are presented with particular emphasis on SBDs and trench MOSFETs we developed.

Image sensor with new trench-gated phototransistor

Abstract: Here we present an image sensor with a new type of phototransistor that realizes a wide dynamic range for photons. The proposed phototransistor has a new function of dynamic range compression, so that the output signal is not limited by the power supply voltage.

Nanostructure fabrication through a microwire of local anodization

Abstract: An aluminum microwire was locally anodized to form a nanowire with triangular cross section. Nanostructure formed through local anodization depended strongly on a cross sectional shape of a microwire before anodization. The width of the nanowire was controlled by the ratio of voltage between edges of locally anodized area to anodization current. This indicates that local anodization has the potential to fabricate of nanostructures for nanodevices.

A fast microwave correlated imaging method based on strip division in large scenes

Abstract: A fast correlated imaging method based on strip division in large scenes is proposed. By transmitting narrow-pulse random signals synchronously from random radiation radar array, the whole imaging area is divided into multiple strips in range direction, then correlated imaging model in strip mode is established, which reduces the scale of its imaging matrix equation greatly; By multi-strip stitching, a whole correlated imaging in a large scene can be achieved; Numerical simulations validate its effectiveness in reducing its imaging time dramatically meanwhile improving its image quality.

Multilevel resistance switching phenomena observed in the Cu (Ti)/HfO 2 /Au device

Abstract: Memory devices having multiple resistance states is promising for increase of memory capacity as well as realizing higher functionality. In this study, we studied multiple resistance states appearing in the reset operation mode in the Cu/HfO 2 /Au and Ti/HfO 2 /Au ReRAM devices. Both devices showed bipolar resistance switching property. Ti/HfO 2 /Au device showed multiple resistance states strictly dependent on the amount of reset voltage, on the other hand, resistance of Cu/HfO 2 /Au device did not show clear dependence on the reset voltage.

Thermal analysis of pulsed LED lighting in Plant Factory

Abstract: LED lighting is studied for Plant Factory because of suitable wavelength and high speed switching. The pulsed LED operating can reduce consumption power of lighting and operating temperature of LED is calculated and measured. Asymmetric pulse shape is tested for lettuce cultivation.

Low-power CMOS LNA for 900-MHz LoRa application through parallel-RC feedback

Abstract: In this paper, a two-stage design of a parallel-RC feedback low-power low-noise amplifier (LNA) that can be used in long-range (LoRa) applications is presented. The first stage involes a common-source amplifier intended to decouple the noise figure (NF). To obtain broadband input matching, a parallel resistance-capacitance shunt feedback is proposed. Furthermore, a source inductance is used to boost the range of adjustments between the gain and noise circle. The second stage involves achieving a higher gain with a cascade architecture. The gain(S21), output return loss(S22), and NF of the LNA were 17.5 dB, −23.3 dB, and 2.6 dB. The power dissipation is 7.2mW. The LNA was simulated in the Advanced Design System (ADS) software and fabricated using a TSMC 1P6M 0.18µm CMOS process.

High breakdown voltage vertical GaN p-n junction diodes using guard ring structures

Abstract: New guard ring structures were adopted to increase the breakdown voltages of the vertical GaN p-n diodes. With this structure, a voltage drop occurs in the guard ring portions by inserting resistance devices between the guard ring portions and the main p-n diode portions, and it is possible to attain higher breakdown voltages by the voltage drop at the most sensitive outer region of the diodes. By adopting this structure, the breakdown voltages of about 200 V has been improved compared with the normal circular p-n diodes.

Sensitivity of piezoelectric MEMS ultrasonic sensors using sol-gel PZT films prepared through various pyrolysis temperatures

Abstract: Sensitivity of piezoelectric ultrasonic microsensors was investigated with sol-gel derived piezoelectric lead-zirconate-titanate (PZT) films under various pyrolysis temperatures. The sensors were fabricated on thin diaphragm structures, whose buckling deflection strongly affects the sensitivity and is controlled through stress of the PZT film. The pyrolysis temperature in the sol-gel process was varied in the range from 250°C to 400°C, and the prepared PZT films on 2-inch wafers were evaluated in crystalline orientation and the stress. The sensor structures were then fabricated on the wafers, and the buckling deflection and the sensitivity of the sensors were evaluated. The stress of the films decreased with increasing the pyrolysis temperature. The preferred crystalline orientation switched from (111) to (100) between the pyrolysis temperatures below and at 400°C. The sensors with the 400°C-pyrolyzed PZT showed much larger buckling deflection and much higher sensitivity than those with PZT pyrolyzed at the lower temperatures.

Investigation of thermal runaway of reverse-biased silicon carbide schottky barrier diode

Abstract: SiC devices are expected to operate at much higher temperature than Si devices. However, commercially available SiC devices are limited to the temperature almost same as Si devices. In order to operate SiC devices at high temperature, it is necessary to improve package technology and to design SiC devices properly for high temperature. In this study, robustness against thermal runaway of SiC-SBD is evaluated. SiC-SBD with a heat-sink is thermally stable, and can operate even at T a = 250 °C without thermal runaway.

Silicon neuronal networks - another approach to intelligent systems

Abstract: Silicon neuronal networks are electronic version of neuronal cells' network. It is a candidate of the fundamental technology of the future information processing systems which can process natural data autonomously, adaptively, and power-efficiently. Two challenges in this field is the implementation-efficient neuronal models and the analog memory device for storing of synaptic efficacy.

MEMS based fabrication of conformal electrode pairs for thermotunneling cooling

Abstract: We developed a microelectromechanical system to controllably fracture overhanging silicon micro-beams, in an attempt to fabricate conformal electrode pairs. Controlled fracture by applying tensile force in the crystal direction produces flat, and very low roughness fracture surfaces, which are then utilized as conformal electrodes for inducing large area tunneling emission of electrons. In tunneling emission, electrons with higher energy have larger tunneling probability (across a nanosize barrier), which can be exploited for selectively tunneling higher energy electrons, causing a cooling effect: referred to as thermotunneling cooling. However, owing to extremely localized nature of tunneling emission, it is difficult to achieve significant cooling for practical purposes. Fracture fabricated electrodes, by complementing surface irregularities on both sides, is expected to overcome this problem. The emission characteristic acquired from the nanogap shows direct and field induced tunneling. A significant hysteretic behavior is also observed. Being a purely solid-state microscale device, its integration in electronic chips and sensors, whose efficacy is often associated with heat dissipation, is relatively easy.

Wearable, healthcare sensor sheets

Abstract: Healthcare is one of important factors for persons to keep their happiness during daily life. In order to maintaining good health conditions, daily continuous health monitoring is effective to find small symptoms before causing severe conditions. In this study, wearable, healthcare sensor sheets are proposed to monitor health conditions and activity, simultaneously, consisted of a skin temperature sensor, an electrocardiogram sensor, an ultraviolet sensor, a pH sweat sensor, and/or a three-axis acceleration sensor on a flexible film. The sensor sheets are fabricated by mainly printing methods in order to realizing macroscale and low-cost electronics. After characterizing each sensor, as a proof-of-concept demonstration, simultaneous human condition monitoring is conducted by attaching the device onto a volunteer's chest.

Optical absorption properties of Ni 1−x Mg x O thin films

Abstract: Optical absorption properties of Ni 1−x Mg x O are studied in the wide energy range from 3.0 to 7.4eV, resulting in the observations of absorption levels of larger than 5.5eV. The absorption levels in the photon energy of less than 5.0eV, reported so far, are attributable to the 2p-3d charge transfer transitions, and the absorption in the large photon energy, observed this time, is owing to the 2p-4s transitions. The energy levels due the 2p-4s transitions can be extrapolated to that of MgO, 7.4eV.

Characterization of AlGaN/GaN HEMTs with directly regrown AlGaN barrier layer

Abstract: This paper demonstrates successful fabrication of AlGaN/GaN high-electron-mobility transistors (HEMTs) with an AlGaN barrier layer directly regrown on a reactive-ion-etched GaN layer. The HEMT device fabricated on a high-mobility (>1000 cm2/Vs) GaN channel exhibited fairly excellent pinched-off characteristics with a maximum drain current of 90 mA/mm, whereas the device fabricated on a low-mobility (<500 cm2/Vs) channel exhibited non-pinch-off leaky characteristics. SIMS measurements indicated accumulation of donor impurities at the AlGaN/GaN interface, indicating intense remote ionized impurity scattering is responsible for the reduced channel mobility.