ULVAC Taiwan Inc.

Hsinchu, Taiwan

ULVAC Taiwan Inc.

Hsinchu, Taiwan
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Wong Y.-Y.,National Chiao Tung University | Chang E.Y.,National Chiao Tung University | Yang T.-H.,National Chiao Tung University | Chang J.-R.,National Chiao Tung University | And 5 more authors.
Journal of the Electrochemical Society | Year: 2010

The role played by different types of threading dislocations (TDs) on the electrical properties of AlGaN/GaN heterostructure grown by plasma-assisted molecular beam epitaxy (MBE) was investigated. Samples with different defect structures and densities were prepared and measurements were taken from the same sample to study the correlative behavior of various TDs. From the Hall measurement, the electron mobility in two-dimensional electron gas channel was mainly controlled by the edge dislocation, which has a dominant amount in the material. The edge TDs acted as Coulomb scattering centers inside the channel and reduces the carrier mobility and increased its resistance. Screw TDs played a much significant role than edge TDs in determining the reverse-bias leakage current of Schottky barrier diodes. Leakage current is affected slightly by the reduction of free carrier density in the channel for samples with a higher edge TD density, but screw TD, which acted as the current leakage path, was more deleterious to the reverse-bias leakage current of AlGaN/GaN structure. © 2010 The Electrochemical Society.

Wong Y.-Y.,National Chiao Tung University | Huang W.-C.,National Chiao Tung University | Trinh H.-D.,National Chiao Tung University | Yang T.-H.,National Chiao Tung University | And 3 more authors.
Journal of Electronic Materials | Year: 2012

AlGaN/GaN structures were regrown on GaN templates using plasma- assisted molecular beam epitaxy (PA-MBE). Prior to the regrowth, nitridation was performed using nitrogen plasma in the MBE chamber for different durations (0 min to 30 min). Direct-current measurements on high-electron-mobility transistor devices showed that good pinch-off characteristics and good interdevice isolation were achieved for samples prepared with a 30-min nitridation process. Current-voltage measurements on Schottky barrier diodes also revealed that, for samples prepared without nitridation, the reverse-bias gate leakage current was approximately two orders of magnitudes larger than that of samples prepared with a 30-min nitridation process. The improvement in the electrical properties is a result of contaminant removal at the regrowth interface which may be induced by the etching effect of nitridation. © 2012 TMS.

Ku J.-T.,National Chiao Tung University | Yang T.-H.,National Chiao Tung University | Chang J.-R.,National Chiao Tung University | Wong Y.-Y.,National Chiao Tung University | And 3 more authors.
Japanese Journal of Applied Physics | Year: 2010

Strain-free gallium nitride (GaN) overgrowth on GaN nano-rods is realized by RF-plasma assisted molecular beam epitaxy (RF-MBE) on silicon (Si) substrate. The strain-free condition was identified by the strong free A exciton (FX A) photoluminescence (PL) peak at 3.478 eV and the E2 high phonon Raman shift of 567 cm-1. It is clearly demonstrated that the critical diameter of GaN nano-rods is around 80nm for the overgrowth of strain-free GaN. The blue-shift of PL peak energy and phonon Raman energy with decreasing the diameter of nano-rod result from the strain relaxation of overgrowth GaN. © 2010 The Japan Society of Applied Physics.

Wong Y.-Y.,National Chiao Tung University | Chang E.Y.,National Chiao Tung University | Wu Y.-H.,National Chiao Tung University | Hudait M.K.,Virginia Polytechnic Institute and State University | And 7 more authors.
Thin Solid Films | Year: 2011

A GaN buffer layer grown under Ga-lean conditions by plasma-assisted molecular beam epitaxy (PAMBE) was used to reduce the dislocation density in a GaN film grown on a sapphire substrate. The Ga-lean buffer, with inclined trench walls on its surface, provided an effective way to bend the propagation direction of dislocations, and it reduced the dislocation density through recombination and annihilation processes. As a result, the edge dislocation density in the GaN film was reduced by approximately two orders of magnitude to 2 × 108 cm- 2. The rough surface of the Ga-lean buffer was recovered using migration enhanced epitaxy (MEE), a process of alternating deposition cycle of Ga atoms and N2 radicals, during the PAMBE growth. By combining these two methods, a GaN film with high-crystalline-quality and atomically-flat surface can be achieved by PAMBE on a lattice mismatch substrate. © 2011 Elsevier B.V. All rights reserved.

Chiu C.-H.,National Chiao Tung University | Tu P.-M.,National Chiao Tung University | Lin C.-C.,National Chiao Tung University | Lin D.-W.,National Chiao Tung University | And 9 more authors.
IEEE Journal on Selected Topics in Quantum Electronics | Year: 2011

We presented a study of high-performance GaN-based light emitting diodes (LEDs) using a GaN nanopillars (NPs) structure grown on sapphire substrate by integrating RF-plasma molecular beam epitaxy (MBE) and metal-organic chemical vapor deposition (MOCVD). Nanoscale air voids were clearly observed at the interface between GaN NPs and the overgrown GaN layer by cross-sectional scanning electron microscopy. It can increase the light-extraction efficiency due to additional light scattering. The transmission electron microscopy images suggest the air voids between GaN NPs introduced during nanoscale epitaxial lateral overgrowth of GaN can suppress the threading dislocation density. Moreover, Raman spectrum demonstrated that the strain of the GaN layer grown on GaN NPs was effectively eliminated, resulting in the reduction of quantum-confined Stark effect in InGaN/GaN quantum wells. Consequently, the LEDs fabricated on the GaN NPs template exhibit smaller electroluminescent peak wavelength blue shift and great enhancement of the light output (70 at 20 mA) compared with the conventional LEDs. © 2011 IEEE.

Lien C.-Y.,Feng Chia University | Chen C.-F.,Feng Chia University | Yang C.-L.,Feng Chia University | Kawai Y.,Feng Chia University | And 6 more authors.
Vacuum | Year: 2015

We produced a VHF H2 plasma (frequency, 60 MHz) by a narrow-gap discharge and examined the plasma parameters as a function of pressure and power, where two parallel plate electrodes (400 × 300 mm2) were used. The plasma density reached a peak at a certain pressure, and when the power was increased, the peak pressure at which the density reached this peak shifted to higher pressures. Measured sheath potentials were lower than the theoretical values while the electron temperature was relatively high. An estimation of plasma uniformity was attempted by measuring the ion saturation current distribution, and the uniformity of about 4% was achieved. © 2015 Elsevier Ltd.All rights reserved.

Chen K.-C.,Feng Chia University | Chiu K.-F.,Feng Chia University | Chen C.-F.,Feng Chia University | Lien C.-Y.,Feng Chia University | And 8 more authors.
Plasma Processes and Polymers | Year: 2016

A capacitively coupled VHF H2 plasma (60 MHz) was produced by a narrow gap discharge at high pressures, and spatial distributions of the plasma parameters were examined with the Langmuir probe. A bi-Maxwellian electron distribution was observed near the discharge electrode while a Maxwellian one near the center of the inter-electrode gap. The simulation using the PIC code showed that electrons had the Druyvesteyn-like distribution near the discharge electrode. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

ULVAC Taiwan Inc. | Date: 2015-10-21

Phonograph records featuring music; compact discs featuring music; headphones.

Ulvac Taiwan Inc | Date: 2016-03-22

A gramophone record includes a main body and a cladding layer. The main body is made of a polymeric material, and has a base surface and an extending surface which extends downward from the base surface. The extending surface defines a continuous spiral groove in the main body. The cladding layer is formed on the extending surface, and has a Hardness Rockwell C (HRC) of not less than 37.

Ulvac Taiwan Inc. | Date: 2016-03-30

A gramophone record of the present disclosure includes a recording member 3 and a functional member 2. The recording member 3 has a main body 31 that is made of a polymeric material and that defines a receiving area 30 in a center thereof, and at least a groove 32 formed on the main body 31. The functional member 2 is disposed in the receiving area 30 and is made of a material having a density greater than a density of the polymeric material of the main body 31.

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