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Yasushi Iyechika

Bio: Yasushi Iyechika is an academic researcher from Sumitomo Chemical. The author has contributed to research in topics: Epitaxy & Metalorganic vapour phase epitaxy. The author has an hindex of 15, co-authored 51 publications receiving 1370 citations.


Papers
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Journal ArticleDOI
TL;DR: In this article, the propagation mechanism of threading dislocations for different GaN facet structures is investigated, and the distribution and density of the threading disllocations are observed by the growth pit density (GPD) method.

456 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of low pressure MOVPE on epitaxial lateral overgrowth (ELO) was studied in relation to the growth temperature, and the mechanism of the morphological change was discussed based on the stability of the surface atoms.
Abstract: Effects of reactor pressure on the epitaxial lateral overgrowth (ELO) via low pressure MOVPE have been studied in relation to the growth temperature. For the ELO GaN on SiO2 stripes along the 〈11-00〉 direction of the underlying GaN, by decreasing reactor pressures from 500 to 40 Torr or by increasing growth temperatures from 950 to 1050 °C, the (0001) surfaces become broad and the side walls are varied from inclined {112-2} surfaces to vertical {112-0} surfaces. For stripes along the 〈112-0〉 direction, the shapes of ELO GaN are independent of the reactor pressures and the growth temperatures. The mechanism of the morphological change is discussed based on the stability of the surface atoms. Typical ELO GaN layers with two-step growth are demonstrated and characterized in their crystalline properties.

293 citations

Patent
21 Dec 1994
TL;DR: In this paper, a method for manufacturing group III-V compound semiconductors including at least Ga as group III element and at least N as the group V element by using metal-organic compounds of group III elements and compounds having at least n in the molecules thereof as the raw materials is provided.
Abstract: There is provided a method for manufacturing group III-V compound semiconductors including at least Ga as the group III element and at least N as the group V element by using metal-organic compounds of group III elements having at least Ga in the molecules thereof and compounds having at least N in the molecules thereof as the raw materials, and the group III-V compound semiconductor crystals are grown in a reaction tube, and epitaxial layer of crystals are grown on a substrate made of a material different from that of the crystals to be grown, wherein at least one kind of gas, selected from a group consisting of compounds including halogen elements and group V elements and hydrogen halide, is introduced before the growth of the compound semiconductor crystal begins, thereby to carry out gas-phase etching of the inner wall surface of a reaction tube. Epitaxial crystals having good crystallinity and surface morphology can be obtained with good reproducibility without impairing the productivity and stability of the product property.

89 citations

Journal ArticleDOI
TL;DR: In this paper, the epitaxial lateral overgrowth of GaN with a stripe tungsten mask pattern is performed by hydride vapor phase epitaxy (HVPE) and a buried structure of the W mask with a smooth surface is achieved for the stripe mask patterns of and direction.
Abstract: The epitaxial lateral overgrowth (ELO) of GaN with a stripe tungsten (W) mask pattern is performed by hydride vapor phase epitaxy (HVPE) and a buried structure of the W mask with a smooth surface is achieved for the stripe mask patterns of and direction. Optical and crystalline characteristics of the ELO-GaN are investigated by means of cathodoluminescence (CL) imaging and X-ray rocking curves (XRCs). It is found that the CL intensity at 133 K due to the near-band edge emission is stronger in the laterally overgrown region in comparison with that in the normal growth region. The φ-ω scan of XRCs reveals that the tilting of the c-axis is much smaller in the ELO-GaN grown with the W mask than that grown with an SiO2 mask.

54 citations

Patent
26 Mar 2002
TL;DR: In this paper, a GaN-based III-V Group compound semiconductor was constructed using a regrowth method based on the HVPE method to form a second 3-V group compound semiconducting layer having a flat surface on a first 3-v-group compound semicisconductor layer formed with a mask layer.
Abstract: A method for fabricating a GaN-based III-V Group compound semiconductor is provided that utilizes a regrowth method based on the HVPE method to form a second III-V Group compound semiconductor layer having a flat surface on a first III-V Group compound semiconductor layer formed with a mask layer. The method uses a mixed carrier gas of hydrogen gas and nitrogen gas to control formation of a facet group including at least the {33-62} facet by the regrowth, and conducting the regrowth until a plane parallel to the surface of the first III-V Group compound semiconductor layer is once annihilated, thereby fabricating a III-V Group compound semiconductor having low dislocation density.

51 citations


Cited by
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Journal ArticleDOI
Fang Qian1, Silvija Gradečak1, Yat Li1, C.-Y. Wen1, Charles M. Lieber1 
TL;DR: The ability to synthesize rationally III-nitride core/multishell nanowire radial heterostructures opens up significant potential for integrated nanoscale photonic systems, including multicolor lasers.
Abstract: We report the growth and characterization of core/multishell nanowire radial heterostructures, and their implementation as efficient and synthetically tunable multicolor nanophotonic sources. Core/multishell nanowires were prepared by metal-organic chemical vapor deposition with an n-GaN core and InxGa1-xN/GaN/p-AlGaN/p-GaN shells, where variation of indium mole fraction is used to tune emission wavelength. Cross-sectional transmission electron microscopy studies reveal that the core/multishell nanowires are dislocation-free single crystals with a triangular morphology. Energy-dispersive X-ray spectroscopy clearly shows shells with distinct chemical compositions, and quantitatively confirms that the thickness and composition of individual shells can be well controlled during synthesis. Electrical measurements show that the p-AlGaN/p-GaN shell structure yields reproducible hole conduction, and electroluminescence measurements demonstrate that in forward bias the core/multishell nanowires function as light-emitting diodes, with tunable emission from 365 to 600 nm and high quantum efficiencies. The ability to synthesize rationally III-nitride core/multishell nanowire heterostructures opens up significant potential for integrated nanoscale photonic systems, including multicolor lasers.

945 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the development of indium nitride (InN) semiconductors from its evolution to the present day and discussed the most popular growth techniques, metalorganic vapor phase epitaxy and molecular beam epitaxy.
Abstract: During the last few years the interest in the indium nitride (InN) semiconductor has been remarkable. There have been significant improvements in the growth of InN films. High quality single crystalline InN film with two-dimensional growth and high growth rate are now routinely obtained. The background carrier concentration and Hall mobility have also improved. Observation of strong photoluminescence near the band edge is reported very recently, leading to conflicts concerning the exact band gap of InN. Attempts have also been made on the deposition of InN based heterostructures for the fabrication of InN based electronic devices. Preliminary evidence of two-dimensional electron gas accumulation in the InN and studies on InN-based field-effect transistor structure are reported. In this article, the work accomplished in the InN research, from its evolution to till now, is reviewed. The In containing alloys or other nitrides (AlGaInN, GaN,AlN) are not discussed here. We mainly concentrate on the growth, characterization, and recent developments in InN research. The most popular growth techniques, metalorganic vapor phase epitaxy and molecular beam epitaxy, are discussed in detail with their recent progress. Important phenomena in the epitaxialgrowth of InN as well as the problems remaining for future study are also discussed.

815 citations

Patent
23 Oct 2006
TL;DR: In this paper, a p-type n-type semiconductor layer is provided in contact with the other surface of the active layer of a single-quantum well structure and a second n-style semiconductor is provided on the first layer.
Abstract: A nitride semiconductor light-emitting device has an active layer of a single-quantum well structure or multi-quantum well made of a nitride semiconductor containing indium and gallium. A first p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided in contact with one surface of the active layer. A second p-type clad layer made of a p-type nitride semiconductor containing aluminum and gallium is provided on the first p-type clad layer. The second p-type clad layer has a larger band gap than that of the first p-type clad layer. An n-type semiconductor layer is provided in contact with the other surface of the active layer.

683 citations

Journal ArticleDOI
TL;DR: The wet etching of GaN, AlN, and SiC is reviewed in this paper, including conventional etching in aqueous solutions, electrochemical etch in electrolytes and defect-selective chemical etched in molten salts.
Abstract: The wet etching of GaN, AlN, and SiC is reviewed including conventional etching in aqueous solutions, electrochemical etching in electrolytes and defect-selective chemical etching in molten salts. The mechanism of each etching process is discussed. Etching parameters leading to highly anisotropic etching, dopant-type/bandgap selective etching, defect-selective etching, as well as isotropic etching are discussed. The etch pit shapes and their origins are discussed. The applications of wet etching techniques to characterize crystal polarity and defect density/distribution are reviewed. Additional applications of wet etching for device fabrication, such as producing crystallographic etch profiles, are also reviewed.

680 citations

Patent
06 Nov 2009
TL;DR: In this article, a light emitting diode (LED) was manufactured by using a wafer bonding method and a method of manufacturing a LED by using the same wafer-bonding method.
Abstract: Provided is a light emitting diode (LED) manufactured by using a wafer bonding method and a method of manufacturing a LED by using a wafer bonding method. The wafer bonding method may include interposing a stress relaxation layer (33) formed of a metal between a semiconductor layer (20) and a bonding substrate (31). When the stress relaxation layer is used, stress between the bonding substrate and a growth substrate may be offset due to the flexibility of metal, and accordingly, bending or warpage of the bonding substrate may be reduced or prevented.

631 citations