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To investigate the miniband and carrier transport properties in the superlattice structure embedded in the p-i-n GaAs solar cells, photoreflectance, photoluminescence, and photothermal spectroscopies were adopted. Two critical energies corresponding to the energy differences between mini-Brillouin zone edges were estimated for thinnest quantum barrier thickness sample by PR. From the PPT and PL, only...
Surface discharge on solid insulator in vacuum is one of the significant issues in the development of vacuum circuit breakers and vacuum interrupters. By measuring induced current in electrostatic probes behind alumina dielectrics due to explosive electron emission (EEE) at surface flashover inception, we studied transiently formed charge characteristics on the alumina dielectrics in the development...
III–V compound semiconductor quantum dot (QD) optical devices, such as high-power lasers and high-speed modulators, have great potential for the future of telecommunications and quantum cryptographic communication. We developed a top-down method for fabricating InGaAs quantum nanodisks (NDs) arrays by using bio-template and neutral beam etching (NBE) processes. Damage-free InGaAs/GaAs nano-pillar...
Silicon Carbide (SiC) devices have the potential to reduce energy losses in high power applications. However SiC devices have yet to achieve ideal performance levels. The SiC diodes and MOSFETs with advanced trench structures succeeded in improving performance by reduction of the internal electric field. In addition, transfer mold type power modules using SiC devices demonstrated high temperature...
A bus-connected tactile sensor system composed of MEMS-CMOS integrated force sensors was developed. A capacitance-to-digital convertor for force sensing, a data reduction processor and a serial bus communication controller are implemented by a laboratory-designed ASIC (Application Specific Integrated Circuit). These functions enable the tactile sensor to be connected with a serial bus cable, and to...
We experimentally demonstrate a compact and low-loss InP/InGaAsP polarization converter, fabricated by a simple self-aligned process. The mode-conversion of 96% and the excess loss of less than 1.0 dB are obtained over the entire C-band.
InGaAs/GaAsP quantum wells (QWs) have been inserted into a GaAs p-i-n cell aiming at a better current matching of an InGaP/GaAs/Ge tandem solar cell: photon absorption at a longer wavelength range than the GaAs bandedge was attempted while keeping pseudo-lattice-matching to GaAs for the QW structure as a whole. The efficient extraction of photo-generated carriers from the InGaAs wells to an external...
Ohmic I–V characteristics at interface between n-type InAs and n-type Si have been obtained. Single-domain InAs islands (1µm in diameter and 0.5 µm in height) have been grown epitaxially on Si(111) by selective-area MOVPE. After annealing, linear I–V characteristic was observed with excellent reproducibility and the current through the electrode depends on the number of InAs islands beneath the surface...
We propose a simple and efficient off-chip coupler for vertical coupling between optical fibers and InP-based slab waveguides. Etching angle of the waveguide edge is controlled by an etching jig made of SiO2-coated aluminum for ICP-RIE. Simulation shows that maximum 71% coupling efficiency would be obtained by matrix expansion methods.
III-V hetero-integration on silicon is most attractive for lasers, SOAs, and detectors for silicon photonics. InGaAs disks on Si substrate have been grown using micro-channel selective-area metal-organic vapor phase epitaxy. We have measured the luminescent spectra by using the micro-photoluminescence systems and obtained broadband spectra in 1.3–2.1 μm range, suitable for the telecom and the data-communication...
Silicon Carbide (SiC) devices have the potential to reduce energy losses in high power applications. However SiC devices have yet to achieve ideal performance levels. This paper presents SiC diodes and MOSFETs with advanced trench structures. These devices succeeded in improving performance by reduction of the internal electric field. Trench Schottky diodes are able to reduce forward voltage drop...
This paper presents fully-integrated multi-axis piezoelectric-on-silicon kinetic energy harvesters (KEHs) that demonstrate enhanced power output via mechanical frequency upconversion. Mechanical energy is converted to electrical energy by out-of-plane and in-plane devices that are micromachined on the same substrate. The out-of-plane device demonstrates nearly 100× frequency upconversion of 134 Hz...
We demonstrate a compact optical buffer module, comprising an InP 1×8 phased-array switch and a silica-based delay line circuit. Tunable and uniform buffering of up to 21 ns is obtained with a 3-ns temporal resolution.
We have developed SiC trench structure Schottoky diodes and SiC double-trench MOSFETs. We succeeded in improving device performance by the reduction of the electric field through the introduction of the aforementioned trench structures. The threshold voltage of the trench structure Schottky diode is 0.48V smaller than the planar. Also, the lowest on-resistance in SiC MOSFETs was achieved.
Dark current reduction of Ge photodetectors has been investigated by GeO2 passivation and gas-phase doped junction. Ultralow junction and surface leakages indicate the dark current of < 1 nA is achievable in the waveguide geometry.
This paper presents a new principle of color changing pixel by controlling the boundary condition for the surface plasmon polariton resonance on a metallic micro/nano mechanical device. A nanometric wire-grid polarizer was developed by the electron-beam patterning of 100 nm thick aluminum on glass; a pair of such polarizers was stacked with a sub-micron gap, and the separation or the in-plane rotation...
The expectation for SiC devices in advanced power electronics applications for saving energy has been still larger. The 4H-SiC planer MOSFETs with high blocking voltage (1300V) and large current (40A) were fabricated. In addition, we have succeeded in fabricating the larger current (300A) 4H-SiC trench MOSFET with low-on resistance (2.6mΩcm2). And, regarding high-temperature operation, SiC IPMs can...
The expectation for SiC devices in advanced power electronics applications for saving energy has been still larger. The 4H-SiC planer MOSFETs with high blocking voltage (1300 V) and large current (40 A) were fabricated. In addition, we have succeeded in fabricating the larger current (300 A) 4H-SiC trench MOSFET with low-on resistance (2.6 mΩ cm2). And, regarding high-temperature operation, SiC IPMs...
We have been developing new in situ CO2 and pH sensor (Hybrid CO2-pH sensor: HCS) for the cruising AUV. The measurement principle for the CO2 sensor is based on spectrophotometry. The CO2 in the surrounding seawater equilibrates with the indicator solution across the gas permeable membranes. The equilibration process causes a change of pH in the indicator solution, which results in the change of optical...
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