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Author

Takayoshi Maeda

Bio: Takayoshi Maeda 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 11, co-authored 35 publications receiving 825 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 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

Journal ArticleDOI
TL;DR: In this article, an advanced facet-controlled epitaxial lateral overgrowth (FACELO) technique was proposed for obtaining a GaN layer with a low threading dislocation (TD) density.
Abstract: We propose here an advanced facet-controlled epitaxial lateral overgrowth (FACELO) technique for obtaining a GaN layer with a low threading dislocation (TD) density. In the selective-area-growth (SAG) GaN with (11–22) facets, TDs from the underlying GaN are bent horizontally, i.e., toward the or direction. In the advanced FACELO technique, TDs are terminated by SiO2 masks on (11–22) facets. Except for coalescence regions, the TD density of the surface was less than 106 cm-2 for the GaN layer grown by MOVPE using the advanced FACELO technique. The side masks have an additional benefit of contributing to the void formation which facilitates the separation of the thick GaN films from the sapphire substrate.

39 citations

Patent
23 Mar 2001
TL;DR: In this article, a re-growing process using a mask pattern was proposed, and threading dislocations in the re-grown layer were terminated by the voids formed on the pattern.
Abstract: Provided is a method of producing a group III-V compound semiconductor having a low dislocation density without increasing the thickness of a re-grown layer, the method includes a re-growing process using a mask pattern, and threading dislocations in the re-grown layer are terminated by the voids formed on the pattern.

37 citations


Cited by
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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
14 Jan 2003
TL;DR: Semiconductor light emitting devices and methods of producing same are provided in this article, where a substrate has a surface including a difference-in-height portion composed of a wurtzite compound.
Abstract: Semiconductor light emitting devices and methods of producing same are provided The semiconductor light emitting devices include a substrate that has a surface including a difference-in-height portion composed of, for example, a wurtzite compound A crystal growth layer is formed in the substrate surface wherein at least a portion of which is oriented along an inclined plane with respect to a principal plane of the substrate The semiconductor device includes a first conductive layer, an active layer and a second conductive layer formed on the crystal layer in a stacked arrangement and oriented along the inclined place

352 citations

Patent
12 Sep 2005
TL;DR: In this article, the authors present a semiconductor light emitting device, consisting of a plurality of semiconductor layers, including a first semiconductor layer having a first conductivity, an active layer interposed between the first and the second semiconductors, and a non-conductive distributed bragg reflector coupled to the plurality of layers, reflecting the light from the active layer.
Abstract: The present disclosure relates to a semiconductor light emitting device, comprising: a plurality of semiconductor layers, including a first semiconductor layer having a first conductivity, a second semiconductor layer having a second conductivity different from the first conductivity, and an active layer interposed between the first semiconductor layer and the second semiconductor layer, generating light via electron-hole recombination; a first electrode, supplying either electrons or holes to the plurality of semiconductor layers; a second electrode, supplying, to the plurality of semiconductor layers, electrons if the holes are supplied by the first electrode, or holes if the electrons are supplied by the first electrode; a non-conductive distributed bragg reflector coupled to the plurality of semiconductor layers, reflecting the light from the active layer; and a first light-transmitting film coupled to the distributed bragg reflector from a side opposite to the plurality of semiconductor layers with respect to the non-conductive distributed bragg reflector, with the first light-transmitting film having a refractive index lower than an effective refractive index of the distributed bragg reflector.

333 citations

Journal ArticleDOI
TL;DR: In this paper, a freestanding GaN substrate over 2 inches in size was successfully prepared for the first time by hydride vapor phase epitaxy (HVPE) using GaAs as a starting substrate.
Abstract: A freestanding GaN substrate over 2 inches in size was successfully prepared for the first time by hydride vapor phase epitaxy (HVPE) using GaAs as a starting substrate. In the experiment, a GaAs (111)A substrate with a SiO2 mask pattern on its surface was used. A thick GaN layer was grown on the GaAs substrate at 1030°C through the openings in the SiO2 mask. By dissolving the GaAs substrate in aqua regia, a freestanding GaN substrate about 500 µm thick was obtained. The full-width at half maximum (FWHM) in the ω-mode X-ray diffraction (XRD) profile of GaN (0002) plane was 106 arcsec. The dislocation density of the GaN substrate obtained was determined to be as low as 2×105 cm-2 by plan-view transmission electron microscopy (TEM). Hall measurements revealed the n-type conductivity of the GaN substrate with typical carrier concentration and carrier mobility of 5×1018 cm-3 and 170 cm2V-1s-1, respectively.

332 citations

Patent
17 May 2006
TL;DR: In this paper, the fabrication of monolithic lattice-mismatched semiconductor heterostructures with limited area regions having upper portions substantially exhausted of threading dislocations is discussed.
Abstract: Fabrication of monolithic lattice-mismatched semiconductor heterostructures with limited area regions having upper portions substantially exhausted of threading dislocations, as well as fabrication of semiconductor devices based on such lattice-mismatched heterostructures.

326 citations