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SUMMARY The purpose of this paper is to analyze the correlation relationship between the salt contamination environment and the actual damage to electric power distribution equipment caused by two typhoons, 2012 typhoon No. 4 (T1204) and 2011 typhoon No. 15 (T1115). T1204 caused salt contamination damage to voltage–current transformers (VCTs), while the T1115 caused no damage to VCTs installed in a same target area. In this paper, the salt contamination environment during the two typhoons, which includes the maximum wind speed, the accumulated rainfall, and the Na flux, is evaluated by a weather reproduction simulation to discuss the causal relationship between the salt contamination environment and the VCT damage. A damage evaluation model is proposed to evaluate the salt-induced damage risk potential of the VCT for reasonable restoration activity.

We propose a normally-off vertical GaN-based transistor on a bulk GaN substrate with low specific on-state resistance of 1.0 mΩ·cm2 and high off-state breakdown voltage of 1.7 kV. P-GaN/AlGaN/GaN triple layers are epitaxially regrown over V-shaped grooves formed over the drift layer. The channel utilizes so-called semi-polar face with reduced sheet carrier concentration at the AlGaN/GaN interface, which enables high threshold voltage of 2.5 V and stable switching operations. The employed p-type gate does not give any concern of the gate instability. Note that formation of carbon doped insulating GaN layer formed on p-GaN well layer underneath the channel suppresses the punch-through current at off-state between the source and drain, which enables good off-state characteristics. The fabricated high-current vertical transistor achieves successful fast switching at 400V/15A. We also propose a novel vertical GaN-based junction barrier Schottky (JBS) diode with trenched p-GaN region on a bulk GaN substrate. A specific differential on-resistance of the GaN JBS diode is 0.9 mΩ·cm2 while keeping high breakdown voltage of 1.6 kV. These results indicate that the demonstrated vertical GaN devices are very promising for future high power switching applications.

Reliability tests on 600V-rated GaN-based normally-off hybrid-drain-embedded Gate Injection Transistor (HD-GIT) are performed. High-temperature reverse-bias test on HD-GIT reveals that the lifetime is dependent on the leakage current before the reliability test. Acceleration factors for the temperature and reverse bias voltage are extracted. Based on the obtained results, devices are designed so that their lifetimes under Vbs=480V (80% de-rated) at 80°C are longer than 1000 years, which are long enough for most conventional power converter applications. Dynamic high-temperature operation life test is also performed, under which their DC characteristics are within their normal range up to 3600h. In addition, HD-GITs are within their normal range under the similar reliability tests as applied for Si-based power transistors. The physical mechanisms for the reliability of HD-GIT are discussed. We conclude that the OFF-state reliability is explained by the so-called percolation degradation model, and that the hole injection from the p-type GaN embedded in the drain plays an important role to suppress the degradation under hard-switching operation test.

This paper reviews the recent activities for normally-off GaN-based gate injection transistors (GITs) on Si substrates and their application to inverters. Epitaxial growth of the AlGaN/GaN heterostructures with good crystallinity over 200-mm Si substrates with eliminated bowing enables low-cost fabrication of GaN devices with high breakdown voltages. A novel normally-off GaN transistor called as GIT is proposed in which hole injection from the p-type AlGaN gate increases the drain current with low on-state resistance by conductivity modulation. The low on-state resistance in GaN-based devices greatly helps to increase the efficiency of power switching systems. A GaN-based three-phase inverter successfully drives a motor with high efficiency of 99.3% at a high output power of 1500 W. The presented GaN-based devices are expected to greatly help saving energy in the future as an indispensable power switching system.

A normally-off vertical GaN-based transistor on a bulk GaN substrate with low specific on-state resistance of 1.0 mΩ·cm2 and high off-state breakdown voltage of 1.7 kV is presented. P-GaN/AlGaN/GaN triple layers are epitaxially regrown over V-shaped grooves formed over the drift layer. The channel utilizes so-called semi-polar face with reduced sheet carrier concentration at the AlGaN/GaN interface, which enables high threshold voltages of 2.5 V and stable switching operations. Note that formation of carbon-doped insulating GaN layer formed on p-GaN well layer underneath the channel suppresses the punch-through current at off-state between the source and drain, which enables good off-state characteristics. The fabricated high-current vertical transistor achieves successful fast switching at 400V/15A. These results indicate that the demonstrated vertical GaN transistor is very promising for future high power switching applications.

GaN-based normally-off Gate Injection Transistors (GITs) with p-type gate over AlGaN/GaN heterojunction are fabricated on bulk GaN substrates. Thickness of insulating GaN buffer layer is increased up to 16 μm for the presented device from 5 μm for conventional GITs on Si. The thick buffer reduces the parasitic output capacitances, which enables fast turn-off switching. The thick buffer and the use of bulk GaN substrate help to improve the crystal quality of AlGaN/GaN so that the sheet resistance is reduced. Improved crystal quality together with reduced trap density successfully suppresses the current collapse up to 1 kV or higher of the applied drain voltage. The resultant R on Q oss (R on : on-state resistance, Q oss : output charge) as a figure-of-merit for high speed turn-off switching is reduced down to 940 mΩnC that is one third from that of GITs on Si. The resultant turn-off dV ds /dt reaches as large as 285 V/ns that is twice higher than reported values by GITs on Si.

In this paper, we present a state-of-the-art integrated GaN power IC capable of operating in a high frequency (MHz) regime. This realizes system size reduction, 60% maximum, of a power IC. The IC consists of two output power transistors (PT) and two gate drivers (GD). The key devices in the IC are normally-off gate injection transistors (GITs) for PT and GD and a normally-on hetero-junction field effect transistor (HFET) for GD. Novel local control of carrier concentration of an identical 2 dimensional electron gas (2DEG) at an AlGaN/GaN interface which made integration of the transistors with such a large threshold voltage difference possible is described. A specially developed post-passivation interconnection process giving low parasitic components is also described. The IC applied to a 12V–1.8V DC-DC converter shows high frequency switching operation well beyond the limit of Si pointing to future improvement in consumer electronics power supply systems.

For realizing a premixed charge compression ignition (PCCI) engine, the effects of bio-ethanol blend oil and exhaust gas recirculation (EGR) on PM-NOx trade-off have been investigated in a single cylinder direct injection diesel engine with the compression ratio of 17.8. In the present experiment, the ethanol blend ratio and the EGR ratio were varied focusing on ignition delay, premixed combustion, diffusive combustion, smoke, NOx and the thermal efficiency. Very low levels of 1.5 [g/kWh] NOx and 0.02 [g/kWh] PM, which is close to the 2009 emission standards imposed on heavy duty diesel engines in Japan, were achieved without deterioration of the thermal efficiency in the PCCI engine operated with the 50% ethanol blend fuel and the EGR ratio of 0.2. It is found that this improvement can be achieved by formation of the premixed charge condition resulting from a longer ignition delay. A marked increase in ignition delay is due to blending ethanol with low cetane number and large latent heat, and due to lowering in-cylinder gas temperature on compression stroke based on the EGR. It is noticed that smoke can be reduced even by increasing the EGR ratio under a highly premixed condition.

Stacked gate dielectrics consisting of wide bandgap SiO2 insulators and thin aluminum oxynitride (AlON) interlayers were systematically investigated in order to improve the performance and reliability of AlGaN/GaN metal–oxide–semiconductor (MOS) devices. A significantly reduced gate leakage current compared with that in a single AlON layer was achieved with these structures, while maintaining the superior thermal stability and electrical properties of the oxynitride/AlGaN interface. Consequently, distinct advantages in terms of the reliability of the gate dielectrics, such as an improved immunity against electron injection and an increased dielectric breakdown field, were demonstrated for AlGaN/GaN MOS capacitors with optimized stacked structures having a 3.3-nm-thick AlON interlayer.

In order to investigate the distribution of droplet sizes in the core region of diesel fuel spray, instantaneous measurement of droplet sizes was conducted by an advanced laser 2-focus velocimeter (L2F). The micro-scale probe of the L2F is made up of two foci and the distance between them is 36 µm. The tested nozzle had a 0.2 mm diameter single-hole. The measurements of injection pressure, needle lift, and crank angle were synchronized with the measurement by the L2F at the position 10 mm downstream from the nozzle exit. It is clearly shown that the droplet near the spray axis is larger than that in the off-axis region under the needle full lift condition and that the spatial distribution of droplet sizes varies temporally. It is found that the probability density distribution of droplet sizes in the spray core region can be fitted to the Nukiyama-Tanasawa distribution in most injection periods.

In order to investigate the effect of transient needle opening on early stage of spray behavior, simultaneous measurements of velocity and size of droplet were conducted by a newly developed laser 2-focus velocimeter (L2F). The micro-scale probe of the L2F was consisted of two foci with a distance of 36 µm. The tested nozzle had a single hole with a diameter of 0.2 mm. The measurements of injection pressure, needle lift, and crank angle were synchronized with the spray measurement by the L2F at the position 10 mm downstream from the nozzle exit. It has been clearly shown that the velocity and size of droplet increase with needle valve opening and that the probability density distribution of droplet size can be fitted to the Nukiyama-Tanasawa distribution under the transient needle opening condition.

A vertical InGaN-based blue light emitting diode (LED) with a reflective metal electrode and thick gold plated base free from insulating sapphire is demonstrated. A 50 μm-thick gold plated layer on a highly reflective platinum p-side ohmic contact is formed on the InGaN-based LED epi-structure, followed by irradiation with high power ultra-violet pulsed laser from the backside of the original sapphire substrate. The laser processing, so called laser lift-off technique, enables the separation of sapphire by decomposition of interfacial GaN layer. No transparent electrode is necessary for the LED because the current can spread well through the highly conductive n-GaN layer so that uniform blue light is emitted through the n-GaN layer. The electroluminescence (EL) spectra show small multi peaks due to the resonance within the formed vertical cavity. In addition, the measured thermal resistance of the vertical LED is smaller than that of the conventional LED on poor heat-conductive sapphire. The vertical LED would increase the brightness together with smaller chip size and lower series resistance. This would be advantageous espacially for high power and highly efficient LEDs applicable to future solid state lighting. (© 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A very thin 1 μm-thick Al 0.11 Ga 0.89 N film is successfully separated from a sapphire substrate by thermal decomposition of interfacial region using high power laser, so-called laser lift-off technique. The used layer structure prior to the separation is 1.0 μm Al 0.11 Ga 0.89 N/0.3 μm GaN on sapphire grown by metal organic chemical vapor deposition (MOCVD), and third harmonic Q-switched Nd:YAG laser ( λ =355 nm) is irradiated from the backside of the sapphire. Absorption of the laser light occurs only at the GaN interlayer and the decomposed thickness is limited up to the interlayer thickness. As a result, a crack-free thin AlGaN film is separated from sapphire with metal Ga underneath through the optimization of the process parameters. In contrast, removal of 2 μm-thick GaN single layer from sapphire is also tested, where peeling-off of the film with cracks is seen. In addition, slight red shift of the peak energy in the cathodoluminescence (CL) spectra of the AlGaN film is observed after the lift-off process, which is due to the relaxation of compressive stress in the film. Thus, separated AlGaN film is free from the disadvantages of using sapphire substrates such as the thermal mismatch, higher series resistance and poor heat dissipation so that it would enable high performance AlGaN-based ultraviolet (UV) light emitters.

A normally-off AlGaN/GaN MOS heterojunction field-effect transistor (MOS-HFET) with a recessed gate structure formed by selective area regrowth is demonstrated. The fabricated MOS-HFET exhibits a threshold voltage of 1.7 V with an improved hysteresis of 0.5 V as compared with a device fabricated by a conventional dry etching process. An analysis of capacitance–voltage (C–V) characteristics reveals that the dry etching process increases interface state density and introduces an additional discrete trap. The use of the selective area regrowth technique effectively suppresses such degradation, avoiding the MOS interface from being exposed to dry etching. The results presented in this paper indicate that the selective area regrowth technique is promising for the fabrication of normally-off AlGaN/GaN MOS-HFETs.

GaN-based Gate Injection Transistors (GITs) with p-type gate over AlGaN/GaN heterojunction serve normally-off operations with low on-state resistances owing to the conductivity modulation by injection of holes. Established basic technologies on the GIT have shown promising features for switching applications. Further improvement of the performances would extend the applications and lead to the widespread use. In this paper, recent technologies on the GITs to improve the performances and extract the full potential are described. These include extension of the wafer diameter of Si up to 8 inch, InAlGaN quaternary alloy to reduce the series resistances, shortening the gate length to improve the device performances, integration of the gate driver and flip-chip assembly for faster switching.

In this paper we will describe a solution to test I/O cells that use four level pulse amplitude modulation (PAM-4) at data rates of 32 Gbaud using a commercial ATE platform without any external instruments. The solution is based on an active test fixture where a retimed digital to analog converter (DAC) is used to generate the PAM-4 stimulus signaling. The comparator side is implemented using a single differential comparator and three consecutive functional tests with different patterns and compare threshold voltages.

In this paper, we present a novel compact DC-DC converter IC in which normally-off GaN-GITs (Gate Injection Transistors) and gate drivers are integrated into one chip. The DC-DC converter IC can achieve higher efficiency and smaller chip size by reducing parasitic inductances between switching power devices and gate drivers. The gate driver, having a DCFL (Direct Coupled FET Logic) with a buffer amplifier which is consisted of a GaN-HFET (Hetero-junction FET) and GaN-GITs can operate with higher speed and lower power consumption. The fabricated DC-DC converter IC exhibits a peak efficiency as high as 86.6% at 2MHz for the 12V-1.8V conversion.

The three-dimensional flow behavior in a low pressure steam turbine under the low load operation was analyzed numerically by applying the Modified FLIC (Fluid In Cell) method to the quasi three-dimensional flow computation. And it was also measured by using the five-hole Pitot probe in the scale-model turbine with the last stage. By comparing the calculated flow angles with the measured ones at the inlet and exit of the rotor, it is shown that the present computation method is a useful skill to predict an occurrence of the reverse flow in the last stage under the low load operation. Both calculated and experimental results show that the reverse flow occurs at the root of the rotor, if the axial exhaust Mach number becomes smaller than 0.3 even though the stator works well.

Si submonolayer-by-submonolayer epitaxy or subatomic-layer epitaxy (SALE) from Si 2 H 6 on Si(001) has been carried out by repeating Si 2 H 6 exposure and surface excitation induced by the combination of substrate resistive heating and Ar + laser irradiation. As the average substrate temperature or the laser irradiation power increases, the surface morphology of a grown film changes from a convex shape to a concave shape through a trapezoid shape. The roughness of a flat area of the trapezoid film is within ±2A˚per growth thickness of 100A˚, and a substrate temperature window of∼ 15°C and a laser power window of∼ 0.25W, where such a flat growth surface and a constant growth rate are obtained, has been observed. The ranges of these windows have been estimated to correspond to the same variation of the surface temperature in the laser irradiation area during the laser irradiation. This result together with the result of the analyses on growth thickness distribution profiles suggests that the laser irradiation works as a thermal effect. Thus, in the Ar + -laser-assisted SALE method, the growth surface morphology then the growth mode is controlled by the surface temperature during the laser irradiation. An Ar + laser is a useful tool to control the surface temperature.

The superior physical and electrical properties of aluminum oxynitride (AlON) gate dielectrics on AlGaN/GaN substrates in terms of thermal stability, reliability, and interface quality were demonstrated by direct AlON deposition and subsequent annealing. Nitrogen incorporation into alumina was proven to be beneficial both for suppressing intermixing at the insulator/AlGaN interface and reducing the number of electrical defects in Al2O3 films. Consequently, we achieved high-quality AlON/AlGaN/GaN metal–oxide–semiconductor capacitors with improved stability against charge injection and a reduced interface state density as low as 1.2 × 1011 cm−2 eV−1. The impact of nitrogen incorporation into the insulator will be discussed on the basis of experimental findings.

Kinetic studies on the current collapse of a normally-OFF AlGaN/GaN heterostructure gate-injection transistor (GIT) subject to current collapse have been performed above room temperature. The current collapse becomes more severe as the temperature increases, for which we clarified the physical mechanism based on a device simulation study that the hole traps in the epilayer play an important role. As the temperature increases, hole emission from the hole traps is stimulated, which causes sharper potential bending on the drain side in the OFF state, leading to more severe current collapse. The detailed dynamics of holes and the resultant energy profiles in the switching are discussed.

A newly developed stratified fuel-water-injection system has been tested for NOx reduction, targeting the future strict restrictions to be set for slow-speed cross-head marine diesel engines. In addition to this system, we have developed anothor possible measure of a direct water injection system. We introduce the details of various test results in comparison to stratified fuel-water-injection system, and also discuss the expected effects on cylinder lubrication of the two different water-injection systems.

We have recently proposed a sub-atomic-layer epitaxy technique (SALE) with which Si is grown by sub-monolayer-by-sub-monolayer from Si 2 H 6 on Si(001). With a newly incorporated surface thermal excitation process, the growth surface is atomically flattened every growth cycle without depending on the saturation coverage of Si 2 H 6 . To optimize SALE growth conditions, the surface flattening reaction process has been investigated by observing time-dependent dynamic changes in reflection high energy electron diffraction (RHEED) patterns during annealing Si 2 H 6 -exposed Si(001) surfaces using a charge-coupled-device camera. Upon annealing, a spotty 2 × 1 pattern of the initial surface changes to a streaky 2 × 1 pattern and then changes to a spotty 2 × 1 pattern again. In the period when the RHEED pattern is streaky, terraces are considered to emerge and grow by adatom migration accompanied by or following hydrogen desorption. On the basis of these RHEED studies, the thichness distribution profiles of films, grown by the SALE method using an Ar + ion laser as a surface excitation source, have been investigated. From the results of the RHEED and SALE growth studies, the relation between the surface excitation conditions and the surface flattening reaction process in the SALE method is obtained.

An ultrahigh-speed 32 K ×8/×9 TTL bi-CMOS SRAM with a 5-ns standard access time was developed using a five-layer polysilicon/two-layer aluminum 0.6-μm bi-CMOS process with 4.2 × 5.6-μm2 4-M SRAM-class small-size memory cells, ultrahigh capacity, self-aligned bipolar electrodes with 18.5-GHz cutoff frequency and 0.6-μm/0.7-μm (nMOS/pMOS) gate-length MOS transistors. This fast access time was achieved by using center power pin-out to reduce output noise, a major problem in the TTL SRAM, together with alternated bit line load architecture, a memory array architecture well suited to center power pin-out. Also used were a bit-line load circuit for rapid precharging of the bit line and a high-speed wired-OR column-sensing circuit.

We present a novel GaN-based diode with low reverse leakage current which ensures the high voltage operation up to 600V. The diode consists of multi-junctions of AlGaN/GaN with a p-GaN overlayer where the anode and cathode are formed on the sidewalls of the channels. The tunneling current which is the origin of the leakage current can be reduced by controlling the potential barrier at the anode sidewall by means of the depletion layer from the p-GaN. The fabricated GaN diode with the p-type barrier controlling layer (BCL) exhibits high forward current of 18A at 1.5V with the breakdown voltages over 600V taking advantages of the reduced leakage current. The fabricated GaN-based diode has smaller R on C of 70 pΩF than 95 pΩF of the commercially available SiC Schottky barrier diode (SBD) indicating that the GaN diode is suitable for power switching. The GaN diode exhibits high conversion efficiency of 98.2 % in the voltage boosting converter at the output voltage of 400V by combining it with a GaN Gate Injection Transistor (GIT). The obtained performance by using the GaN diode is superior to that with a SiC SBD.

In this paper, we present a successful operation of Gallium Nitride(GaN)-based three-phase inverter with high efficiency of 99.3% for driving motor at 900W under the carrier frequency of 6kHz. This efficiency well exceeds the value by IGBT (Insulated Gate Bipolar Transistor). This demonstrates that GaN has a great potential for power switching application competing with SiC. Fully reduced on-state resistance in a new normally-off GaN transistor called Gate Injection Transistor (GIT) greatly helps to increase the efficiency. In addition, use of the bidirectional operation of the lateral and compact GITs with synchronous gate driving, the inverter is operated free from fly-wheel diodes which have been connected in parallel with IGBTs in a conventional inverter system.

A L2F (Laser 2-Focus velocimeter) was applied for the measurements of the velocity and size of droplets in diesel fuel sprays. The micro-scale probe of the L2F has an advantage in avoiding the multiple scattering from droplets in a dense region of fuel sprays. A data sampling rate of 15MHz has been achieved in the L2F system for detecting almost all of the droplets which passed through the measurement probe. Diesel fuel was injected into the atmosphere by using a common rail injector. Measurement positions were located in the planes 15, 20, and 25 mm apart from the injector nozzle exit. Measurement result showed that the integral time scale of turbulence in size was nearly the same as the one in frequency. And the integral time scale of turbulence in velocity was about two times larger than the time scale of size and frequency.Copyright © 2011 by JSME

We propose a novel technique to boost the blocking voltage of AlGaN/GaN hetero junction field effect transistors (HFETs) by widening a depletion layer in highly resistive Si substrate. The blocking-voltage boosting (BVB) technology utilizes ion implantation at the peripheral area of the chip as channel stoppers to terminate the leakage current from the interfacial inversion layers at AlN/Si. A depletion layer is widened in the substrate by the help of the channel stopper, which increases the blocking voltage of the HFET. The off-state breakdown voltage of the HFETs is increased up to 1340V by the BVB technology from 760V without the channel stoppers for the epitaxial GaN as thin as 1.4µm on Si. This technology greatly helps to increase the blocking voltage even for thin epitaxial GaN on Si, which leads to further reduction of the fabrication cost.

Recent advances in GaN power switching devices are reviewed. A new normall-off GaN transistor called Gate Injection Transistor (GIT) increases drain current by conductivity modulation. The GIT is fabricated on cost-effective Si substrates by novel MOCVD technology enabling crack-free and smooth surfaces over 6-inch wafer. These technologies with thermally stable device isolation by Fe ion implantation are applied for a monolithic inverter IC. This is the world fist demonstration of a GaN inverter IC for motor drive, which reduces the total operating loss by 42% from that by the IGBT-based inverter. These technologies are indispensable for wide-spread use of GaN power switching transistors in the future.

State-of-the-art device technologies of GaN power switching transistors are reviewed. The presented technologies solve the technical issues on GaN transistors for practical use replacing currently used Si-based power devices. Thick epitaxial growth over 6-inch Si substrates enables low cost fabrication of GaN devices with high breakdown voltages. A new operating principle for the normally-off GaN transistor called Gate Injection Transistor (GIT) is proposed in which hole injection from the p-type AlGaN gate increases the drain current by conductivity modulation. Six GITs are integrated onto a single chip on silicon as the world first GaN-based monolithic inverter IC. The inverter IC successfully drives a motor with low operating loss which is 42% reduced from that of the conventional IGBT (Insulated Gate Bipolar Transistor)-based one. These technologies are indispensable for wide-spread use of GaN power switching transistors in the future.

A semiconductor laser with a wide active stripe was utilized as the power source of a laser 2-focus velocimeter. The focus was expanded to about 0.2mm wide to form the two parallel focal planes. The backscattered light from seeding particles was detected by photodiodes, and the time-of-flight between two foci was counted by means of a digital clock. The flow velocity was measured in a circular jet stream, and the results were compared with those measured simultaneously by Pitot tube. After checking the accuracy of measurements, the blade-to-blade distribution of velocity and flow angle were measured at the exit of a centrifugal impeller to confirm the applicability of the semiconductor-L2F with band focus.

A laser 2-focus velocimeter (L2F) has been applied for the measurements of velocity and size of droplets in the core region of diesel spray. The L2F has a micro-scale probe which consists of two foci. The focal diameter is about 2 μm, and the distance between two foci is 20 μm. The feature of this L2F is that the focus is reduced to near the diffraction limit. Investigated was the fuel spray injected intermittently into the atmosphere from an injector nozzle with the orifice diameter of 0.113 mm. The injection pressure was set at 40 MPa by using a common rail system. Measurement positions were located at 10 to 30 mm apart from the orifice exit along the spray axis. Valid data were extracted by a conditional sampling method based on the fact that a droplet passes through both upstream and downstream foci. Measurement result shows that the velocity and size of droplets decrease with the distance along the spray axis. It is clearly shown that the distance between droplets in isotropically dispersed condition decreases with the distance along the spray axis.Copyright © 2007 by ASME

Current collapse is suppressed up to 800 V of drain voltage in our proposed device, Hybrid-Drain-embedded Gate Injection Transistor (HD-GIT), where an additional p-GaN layer is grown on the AlGaN barrier layer and is connected to the drain electrode. We present, based on a device simulation and electroluminescence study, that the hole injection from the additional drain-side p-GaN at the OFF state compensates the hole emission in the epilayer. As a result, the gate-drain access region is not negatively charged at the OFF state, resulting in the drastic suppression of current collapse in HD-GIT.

Homogeneously charged natural gas was burned in a diesel engine assisted by a small amount of gas oil injection. The effects of the equivalence ratio of natural gas, the intake temperature and the EGR rate on ignition ofgas oil, the burning rate of natural gas and the knock limit were clarified experimentally. As results, a marked improvement in the trade-off between smoke and NOx was obtained maintaining a high thermal efficiency by a combination between the natural gas charge rate, the EGR rate, the intake preheating and the nozzle orifice size suitable at each engine load.

The described technology uses a quintuple poly-Si and double-metal process architecture. The emitter and base of a bipolar transistor are self-aligned. The retrograde well for MOS transistors and the P isolation for bipolar transistors are formed by using high-energy ion implantation, while the concentration of the collector is determined by an N epitaxial layer only. As thick oxide remains at the base region before sidewall formation of MOS transistors, an ideal base current flows. The delay times of ECL, CMOS, and BiNMOS are 87 ps, 97 ps, and 130 ps, respectively. BiNMOS has a speed advantage over CMOS down to 2.5 V. A 5-ns 256 K (32 K*8) TTL SRAM has been fabricated with a 0.6- mu m BiCMOS SRAM technology. >

A new technique using a single CCD image through a lens system with large aberration is proposed in the present study for measurement of the three dimensional position of particles, in which a thick laser light source and a forward-scattering light from particles are processed. This optical system could be very compact and applicable to various flow measurements. The particle image detected by a CCD sensor is distorted in the present system due to lens aberrations. A transformation function of the optical system, which is the relationship between the reference particle with unit luminosity in the measuring volume and the corresponding distorted particle image detected by a CCD sensor through symmetric-convex lenses, is constructed theoretically based on the image formation optics of small particles. In order to obtain a high accuracy in the measurement, it is important to remove the background noise and the light intensity non-uniformity in the measuring volume from the CCD particle image by using a low-pass filtering technique based on the FFT analysis. By calculating the cross-correlation coefficient between the measured particle image and the data base images prepared by the above transformation function, the three dimensional position of the particle is determined as the position at which the largest cross-correlation coefficient is obtained. It is verified experimentally that this compact measuring system is useful for measurement of the three dimensional position of the particle with a good accuracy.Copyright © 2003 by ASME

A GaN-based normally off heterostructure field effect transistor (HFET) with high current density and with a quaternary InAlGaN barrier instead of an AlGaN barrier is investigated. It is difficult to obtain both high-current operation and normally off operation in the GaN-based HFET because of the need to control the polarization-induced charge. In order to obtain a normally off operation using quaternary InAlGaN barrier, the InAlGaN barrier is selectively removed and the p-AlGaN layer is formed as the gate electrode. The obtained threshold voltage of the InAlGaN-based HFET is +1.1 V. The maximum drain current reaches as high as 0.73 A/mm, which is almost twice that of a conventional AlGaN-based normally off gate injection transistor (GIT).

In this paper, recent advances of GaN transistors on Si for switching and high-frequency applications are reviewed. Novel epitaxial structures including superlattice interlayers grown by metal organic chemical vapor deposition (MOCVD) relieve the strain and eliminate the cracks in the GaN over large-diameter Si substrates up to 8 in. As a new device structure for high-power switching application, Gate Injection Transistors (GITs) with a p-AlGaN gate over an AlGaN/GaN heterostructure successfully achieve normally-off operations maintaining high drain currents and low on-state resistances. Note that the GITs on Si are free from current collapse up to 600 V, by which the drain current would be markedly reduced after the application of high drain voltages. Highly efficient operations of an inverter and DC–DC converters are presented as promising applications of GITs for power switching. The high efficiencies in an inverter, a resonant LLC converter, and a point-of-load (POL) converter demonstrate the superior potential of the GaN transistors on Si. As for high-frequency transistors, AlGaN/GaN heterojuction field-effect transistors (HFETs) on Si designed specifically for microwave and millimeter-wave frequencies demonstrate a sufficiently high output power at these frequencies. Output powers of 203 W at 2.5 GHz and 10.7 W at 26.5 GHz are achieved by the fabricated GaN transistors. These devices for switching and high-frequency applications are very promising as future energy-efficient electronics because of their inherent low fabrication cost and superior device performance.

In order to measure the disintegration phenomena of diesel fuel droplet by a compact PIV optical system with variable lighting duration, 15 red super bright LEDs and 15 yellow ones were used for a light source. More electric currents than ten times of the standard were supplied to each LED for increasing the light intensity. A CCD camera was used to record images of glass beads of 30, 60, and 100μm in diameter mixed in the air jet stream. It is clearly shown that the luminosity integration value of a particle image is proportional to the 2nd power of particle diameter. Two images corresponding to two kinds of LED were extracted from the double exposure image of fuel droplets injected in the atmosphere from the diesel fuel injection nozzle. It is clarified that inner droplets is larger than outer droplets in the spray periphery region.