A5101871847- GaN-based semiconductor devices and materials
- Radio Frequency Integrated Circuit Design
- Microwave Engineering and Waveguides
- Physics of Superconductivity and Magnetism
- Advanced Power Amplifier Design
- Semiconductor Quantum Structures and Devices
- Acoustic Wave Resonator Technologies
- Semiconductor materials and devices
- Antenna Design and Analysis
- Particle Detector Development and Performance
- Particle accelerators and beam dynamics
- Advanced Condensed Matter Physics
- Magnetic properties of thin films
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Full-Duplex Wireless Communications
- Magnetic and transport properties of perovskites and related materials
- Advanced MEMS and NEMS Technologies
- Microwave Dielectric Ceramics Synthesis
- Theoretical and Computational Physics
- Superconductivity in MgB2 and Alloys
- Ionosphere and magnetosphere dynamics
- Magnetic confinement fusion research
- Dynamics and Control of Mechanical Systems
- Silicon Carbide Semiconductor Technologies
Shibaura Institute of Technology
2020-2021
National Institutes for Quantum Science and Technology
2020
Tokyo Institute of Technology
2002-2020
Ibaraki University
2020
Kyushu Institute of Technology
2018
Mitsubishi Electric (Japan)
1976-2014
Fujitsu (Japan)
1997-2013
Mitsubishi Group (Japan)
2000-2012
Hitachi (Japan)
1974-2011
Iowa State University
2010
We examined the effect of Ca 2 PbO 4 addition on superconductivity in a Bi-Sr-Cu-O system. determined that is formed Bi-Pb-Sr-Ca-Cu-O at temperatures lower than 750°C basis powder X-ray diffraction and micro-Raman scattering. A high- T c phase was synthesized by adding to system which has single CuO layer. It seems synthesis process based reaction between low- structure 2+ liquid caused decomposition 822°C.
Photocurrent (PC) spectroscopy under high electric fields perpendicular to the heterointerface has been utilized characterize subband structures in GaAs/AlGaAs multiple quantum wells (MQW’s). The PC spectra from MQW’s show clear exciton peaks corresponding forbidden transitions between electron and hole subbands. From spectra, we have precisely determined splitting energies of two lowest four highest subbands 55-, 82-, 105-Å-thick wells. experimental results indicate that conduction-band...
The interaction of water and carbon dioxide with nanostructured epitaxial (Ba,Sr)TiO3(001) thin film bulk single crystal SrTiO3(001) surfaces was studied using x-ray photoemission spectroscopy (XPS), thermal desorption (TDS), density functional theory (DFT). On both surfaces, XPS TDS indicate D2O CO2 chemisorb at room temperature broad peaks (423–723 K) a peak near 573 K. A comparison Redhead activation energies to adsorption calculated DFT indicates that defect surface sites are important...
The thermoelectric power factor of SrTiO3 is unusually high with respect to its mobility and band gap. Good thermoelectrics usually have a narrow gap, but such properties are not found in SrTiO3. We determined the mechanism behind by calculating transport coefficients. key understanding that different effective masses contribute phenomena. discrepancy between mass for conductivity showed conveyed electrons Brillouin zone. Light were responsible conductivity, whereas heavy power. carrier...
Using deep-level transient capacitance spectroscopy we have investigated deep electron traps in n-AlGaAs grown by molecular-beam epitaxy (MBE). The thermal activation energies of seven traps, labeled ME1–ME7, observed this study increase with increasing Al content(x) up to the direct-indirect crossover point (x∼0.42), but show only a small change further increases content. Traps ME4–ME7 are dominant samples x≤0.2. ME4–ME6 strongly depend on growth ambient. concentration ME7 is almost...
A planar multilevel interconnection technology, called metallization with polymer (PMP), has been developed, which utilizes a polyimide known as PIQ (polyimide isoindroquinazoline-dione) an interlevel dielectric. The is highly resistant to heat and mechanically flexible. Its low impurity concentrations also make it very stable in semiconductors. PMP processing techniques have refined the stage where ICs can be fabricated commercially. film etchant forms fine via-holes up 3/spl times/3 /spl...
The electronic structure of ${\text{SrTiO}}_{3}$ single-crystal surfaces and their interaction with ${\text{CO}}_{2}$ at room temperature is studied by angle-resolved x-ray ultraviolet photoelectron spectroscopies (XPS UPS) density-functional theory (DFT). exposure results in spectral features the $\text{O}\text{ }1s$ $\text{C}\text{ core levels a binding-energy separation $\ensuremath{\Delta}{E}_{(\text{O}\text{ }1s\ensuremath{-}\text{C}\text{...
Raman scattering by coupled plasmon--LO-phonon modes has been studied in direct-band-gap n-type ${\mathrm{Al}}_{\mathrm{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathrm{x}}$As epitaxial layers with various carrier concentrations. spectra from (100) surfaces of the exhibit three branches whose frequencies and dampings depend on both concentration alloy composition. The dispersion relations have also investigated use different lines excitation lasers, wave-vector dependence confirmed....
Low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs grown by molecular beam epitaxy has been studied. The defect-related emissions, due to the defect exciton (d, X) and complex (d), have identified. peak energies these which are 1.505 eV 1.474 (d) for GaAs, determined as a function mole fraction x ( x<0.45). energy difference between donor–bound-exciton (BE) defect-exciton is almost constant (∼9 meV). In contrast, BE defect-complex increases from 40 meV at x=0...
In this paper, internally matched GaN-HEMT high power amplifiers operating at X- and Ku-bands are presented. For the X-band amplifier, small package is adopted to reduce over all RF module size. Ku-band 4 transistor bars combined obtain 100W output power. To best of our knowledge, first report that more than obtained from single solid state device in Ku-band.
An idealized mathematical model of a linear elastic Bernoulli-Euler beam, in which each element the beam has an infinitesimal quantity stored angular momentum, is presented. This continuous distribution momentum termed gyricity. The governing equations motion are derived when system subject to conservative external loads. It shown that these systems can display both static instabilities (divergence) and dynamic (flutter), structure stability regions depends on stiffness, gyric stabilization...
We applied a Cat-CVD (catalytic chemical vapor deposition) passivation film to AlGaN/GaN HEMTs, resolve the trade-off between their drain current transient time and gate-drain break down voltage. did not employ any field plate because it degrades high frequency operation over C-band. The SiN film, deposited after NH3 treatment, resulted in less gate leakage than conventional PE-CVD passivation. A T-shaped HEMT fabricated by this technique, with Lg = 0.4 µm Wg 50.4 mm, delivered an output...
In this paper, GaN HEMT high power amplifiers operating at C-band are presented. Improvement of device performance and reduction thermal resistance with larger gate pitch enabled 1.4 times density compared the previous work [1]-[2]. 167 W output was extracted from a single chip 7 W/mm density. 2-chip amplifier have recorded 220 C-band, which is highest ever reported for higher bands.
In this paper are given some recent results on modeling of High Power GaN HEMT devices. The is very promising for high power application, but we push device to the limits, so many issues becoming critical. For example, access resistances Rs, Rd in GAN bias and temperature dependent - their extraction from cold FET measurements can lead over optimistic prediction output power. Thermal management, self-heating another important issue they influence reliability, PAE. Models without dynamic not...
In this paper, a high efficiency C-band GaN HEMT power amplifier with internal harmonic manipulation circuits is presented. We employed new circuit topology for simultaneous matching at both fundamental and 2nd-harmonic frequencies. The developed has achieved over 57% drain (50% power-added-efficiency) 100W output C-band. This the state-of-the-art of to best our knowledge.
Experiments on additional heating by neutral beam injection and application of a low frequency wave to plasma with an extremely high averaged beta value about 90% - field reversed configuration (FRC) are carried out using the FRC Injection Experiment (FIX) apparatus. These experiments made possible translating produced in formation region theta pinch confinement order secure better accessibility facilities control density. By determining appropriate geometry mirror ratio region, it became...
A high Tc phase (Tc ≂110 K) in Bi-Pb-Sr-Ca-Cu-O systems was synthesized by adding Ca2PbOx to the mixture of a low ≂80 and Bi-Sr-Cu-O ≂10 K). X-ray powder diffraction measurement suggests that sintered bulk mainly consists phase. The volume fraction 74% from magnetization. lower critical field Hc1 10 Oe at 77.3 K. current density Jc 3.0×102 A/cm2 obtained for repressed sample with highly oriented microstructure.
We have studied defect-related emissions in low-temperature (∼4 K) photoluminescence of lightly Si-doped AlxGa1−xAs (x<0.45) grown by molecular beam epitaxy. The relative intensities the defect exciton (d,X) and complex (d) depend on mole fraction x; emission becomes dominant for x>0.27. This suggests different origins emissions. are tentatively associated with oxygen carbon, respectively.