IRE Laboratory

The 6th International Symposium on Growth of III nitrides

Hamamatsu, Act City Hamamatsu

The 45th National Conference on Crystal Growth

Hokkaidou University

2015/10/19-21
Growth of GaN on Si using a graded buffer by RF-MBE

2015/10/19-21
Growth of GaN on Si using a graded buffer by RF-MBE

Graded buffer layer (GB) of GaN on Si(G0oS) grown on Si(111) by a radiofrequency discharge molecular beam epitaxy (RF-MBE) was studied to grow high quality GoS films. Interface between GaN and Si was analyzed by XRD 2θ-ω,ω rocking curve, reciprocal space mapping(RMS).
( in Japanese)

2015 Spring Nano epi- sub-section meeting of JACG

The 7th meeting of crystal growth of nitride semiconductor( pre conference of ISGN-6) at Sakura Hall in Tohoku University

2015/5/7-8
Interface Reactive Epitaxial Growth of double buffer layer of AlN on Si and XRD characterization of RF-MBE grown AlN on Si

2015/5/7-8
Interface Reactive Epitaxial Growth of double buffer layer of AlN on Si and XRD characterization of RF-MBE grown AlN on Si

in Japanese

The 44th National Conference on Crystal Growth

(NCCG-44)

2014/11/6-8
Growth of AlN epitaxial film on Si(111) by RF-MBE
- Double buffer layer growth and thickness dependence of film thickness -

2014/11/6-8
Growth of AlN epitaxial film on Si(111) by RF-MBE
- Double buffer layer growth and thickness dependence of film thickness -

Thickness dependence of FWHM of XRD of AlN(0001) grown on Si(111) by a radiofrequency discharge molecular beam
epitaxy (RF-MBE) was studied to grow high quality AlN films. Interference fringe observation on 2theta-omega scan for
thin-high-quality AlN on Si (AoS) films showed growth of nearly perfect crystal of AlN on Si substrate.

ISPlasma2014

The 43 National COnferene on Crystal Growth NCCG-43 Nagano

2013/11/6-8
Growth of AlN epitaxial film on Si(111) by RF-MBE
- Double buffer layer growth and thickness dependence of film thickness -

2013/11/6-8
Growth of AlN epitaxial film on Si(111) by RF-MBE
- Double buffer layer growth and thickness dependence of film thickness -

Thickness dependence of FWHM of XRD of AlN(0001) grown on Si(111) by a radiofrequency discharge molecular beam
epitaxy (RF-MBE) was studied to grow high quality AlN films. Interference fringe observation on 2theta-omega scan for
thin-high-quality AlN on Si (AoS) films showed growth of nearly perfect crystal of AlN on Si substrate.

JSAP-MRS joint symposium J-section

2013/09/16-20
JSAP-MRS joint symposium held at Kyotanabe campus of Doshisha University

2013/09/16-20
JSAP-MRS joint symposium held at Kyotanabe campus of Doshisha University

Interface Reaction Epitaxial (IRE) Growth and Double Buffer Layer (DBL) of AlN on Si using PA-MBE

STARC workshop 2013

ICCGE-17

2013/08/11-18


2013/08/11-18

Poster presentation at the 17th International Conference on Crystal Growth and Epitaxy entitled with Activity modulation and role of nitrogen radicals in RF-MBE for growth of group III nitrides and their alloys

Financial support to Exhibition of IRE Laboratory at ICCGE-17 from Kyotanabe city.

ISPlasma2013

Shimaya Venture Festa 2012

NCCG-42

Business Fair in Kyotanabe 2012

2012/10/11


2012/10/11

Our exsivition was held in Business Fair in Kyotanabe 2012 at Tatara Capmus of Doshisha University.

MBE2012

2012/9/27
Poster presentation was performed in the 17th International Conference on Molecular Beam Epitaxy (MBE2012) in September 23-28, 2012 at Nara Prefectural New Public Hall, Nara, Japan.

2012/9/27
Poster presentation was performed in the 17th International Conference on Molecular Beam Epitaxy (MBE2012) in September 23-28, 2012 at Nara Prefectural New Public Hall, Nara, Japan.

MBE2012 http://mbe2012.jp/

ISGN4

2012/7/15
Prof. Ohachi is going to attend 4th International Symposium on Growth of Symposium on III Nitdires (ISGN4) July 16-19, from July 14.

2012/7/15
Prof. Ohachi is going to attend 4th International Symposium on Growth of Symposium on III Nitdires (ISGN4) July 16-19, from July 14.

His travel is partially supported by Kyotanabe City an a project of the promotion of Excerllent Article of Kyotanabe.
He is going to explain his recent rezsults on activity modulation (AM-MEE) tequnique to grow GaN and AlN on Si substrate using MBE apparatus. ISGN4

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Collaboration study

2012: CrystEngComm, 2012, 14, 5572?5578
Spray drying mass-production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder based on a wet-chemical method

2012: CrystEngComm, 2012, 14, 5572?5578
Spray drying mass-production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder based on a wet-chemical method

Qingbo Liu,a Dehui Sun,a Tao Yan,a Feifei Zheng,b Yunhua Sang,a Hong Liu,*a Jiyang Wanga
and Tadashi Ohachic
aState Key Laboratory of Crystal Materials, Shandong University, Shandanan Road, Jinan, 250100, China bYuanhong Technical Materials Ltd., Jining, China
cDepartment of Electrical Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan

A mass production route for Mg-doped LiNbO3 (Mg:LN) polycrystalline powder was proposed based on a wet-chemical method/spray drying process. A stable homogenous precursor solution was prepared by dissolving commercial Nb(OH)5, Li2CO3 and MgO, and was stabilized with citric acid (CA) as a chelating agent. Spherical Mg:LN precursor powder can be obtained by a spray-drying method, and spherical mono-phase perovskite Mg:LN polycrystalline powder with uniform size was obtained by calcining the precursor powder at relatively low temperature. Thermogravimetry? differential thermal analysis (TG?DTA), X-ray diffraction (XRD), infrared spectroscopy and scanning electron microscopy (SEM) were used to characterize the precursor and product powder. The as-obtained Mg:LN powder was used for Mg:LN single-crystal growth. The obtained Mg:LN single crystal possesses both high optical homogeneity and ingredient uniformity. This mass production route for preparation of Mg:LN powder provides a solution to the problem of defects in Mg:LN single crystals caused by nonhomogeneity of magnesium distribution.

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2012: CrystEngComm, 2012, 14, 1783?1789
Ammonium sulfate regulation of morphology of Nd:Y2O3 precursor via urea precipitation method and its effect on the sintering properties of Nd:Y2O3 nanopowders

2012: CrystEngComm, 2012, 14, 1783?1789
Ammonium sulfate regulation of morphology of Nd:Y2O3 precursor via urea precipitation method and its effect on the sintering properties of Nd:Y2O3 nanopowders

Haiming Qin,a Hong Liu,*a Yuanhua Sang,a Yaohui Lv,b Xiaolin Zhang,a Yuanyuan Zhang,a Tadashi Ohachic and Jiyang Wang*a
aState Key Laboratory of Crystal Materials, Shandong University, Jinan, 250100, China. E-mail: hongliu@sdu.edu.cn; Jywang@sdu.edu.cn; Fax: +86-531-88362807; Tel: +86-531-88362807bSchool of Materials Science and Engineering, Anhui University of Technology, Maanshan, 241002, China cDepartment of Electrical Engineering, Doshisha University, Kyotanabe, Kyoto, 610-0321, Japan

Ammonium sulfate has been widely used as a control agent in the preparation of yttrium-aluminiumgarnet (YAG) transparent ceramics, however, research of its application in the preparation in transparent ceramic yttria has not been intensively studied. Neodymium?doped yttria (Nd:Y2O3) nanopowders with controlled morphology and size were synthesized via a urea precipitation method using ammonium sulfate as the additive. The effect of ammonium sulfate was intensively studied throughout the preparation process. Morphology of precursors was found to be evidently affected by the [(NH4)2SO4]/[Nd:Y2O3] ratio (measured by weight). Uniform spheres of Nd:Y2O3 precursor were obtained without the addition of ammonium sulfate. With increasing amounts of ammonium sulfate added, the scale of the Nd:Y2O3 precursors diminished which results in the aggregation of the Nd:Y2O3 precursor. Aggregates of coral like particles after precipitation and uniform well dispersed particles after calcinations were obtained as the dosage of ammonium sulfate reached 20 wt%. It was consideredto be the optimum state for the preparation of highly sinterable Nd:Y2O3 nanopowders. Ammonium sulfate was proved to be a regulator that could mediate the nucleation and growth of the precursor as well as its decomposition behaviour. Results of this paper can contribute to the controllable synthesis of transparent ceramic yttria.

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Reports 2006〜2010

2010 report (2) (in Japanese)
Interface reaction epitaxial growth of double buffer layer of AlN /β-Si3N4 on Si for growth of group III nitrides using PA-MBE(II)

2010 report (2) (in Japanese)
Interface reaction epitaxial growth of double buffer layer of AlN /β-Si3N4 on Si for growth of group III nitrides using PA-MBE(II)

Double buffer layer (DBL) AlN(0002)/β-Si3N4/Si(111) was developed for the growth of AlN and GaN by plasma assisted molecular beam epitaxy (PA-MBE) method. The DBL was formed the following two reaction epitaxies (IRE). The hexagonal silicon nitride (β-Si3N4) film with 8/3x8/3 or 8x8 surface reconstructions was formed by an IRE. The succesive IRE of AlN, which was formed deposited Al atoms on the β-Si3N4 and N atoms in the β-Si3N4. Al polarity of AlN was successfully grown on the 8x8 reconstruction of β-Si3N4 whereas N polarity of AlN was grown on 8/3x8/3. The reaction procedure of IRE-AlN was studied by the low temperature (LT) Al deposition on the thin β-Si3N4 layer and high temperature (HT) annealing. AlN was formed on β-Si3N4 by the reaction between Al irradiated atoms and N atoms in the β-Si3N4 layer. The reflection high energy electron diffraction (RHEED) patterns from IRE-AlN film indicated the surface of IRE-AlN was very uniform without Si-Al bonds. The both AlN layer on the DBL and GaN film on the AlN buffer layer were grown by the activity-modulation migration enhanced epitaxy (AM-MEE). Hetero epitaxial grown films of GaN (30nm) /AlN buffer(30nm) /DBL/Si(111) were prepared to analyze using a three layers model of grazing incidence-angle X-ray reflectivity (GIXR), which consisted with three layers of GaN, AlN buffer and Si. The polarity of DBL was investigated by the RHEED patterns and KOH etching patterns that the surface was Al polarity and the polarity of thick AlN films grown on DBLs was the same one of DBL. Additional deposition of Al atoms on the Al polar DBL formed a quasi liquid layer (QLL) of Al and the polarity inversion from Al to N polarity of AlN formed in QLL was found.

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2010 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by rf-discharge (III)

2010 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by rf-discharge (III)

During rf discharge adsorbed (ADS) N atoms, which were in a state of local equilibrium, were able to be measured by a self-ionization of ADS atoms on a negatively biased electrode. The ADS flux was measured by a parallel plates electrode or parallel mesh electrode (atom probe), which were biased negatively by the self ionization of N atoms. The atom flux current IA is give by the following equation, IA = -γ SFNEAVA +I0 , where γ is the self ionization coefficient [A/Vm2 ], S [m2 ] is the surface area of the atom electrode, and VA [V] (VA = - EA + VB = - EA - EB < 0 ) is the atom potential, which is negatively biased for the self ionization, EA [V] is potential difference between two plate electrodes, and EB [V] is a bias potential to increase the absolute value of the atom potential.

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2009 report (2) (in Japanese)
Interface reaction epitaxial growth of double buffer layer of AlN /β-Si3N4 on Si

2009 report (2) (in Japanese)
Interface reaction epitaxial growth of double buffer layer of AlN /β-Si3N4 on Si

for growth of group III nitrides using PA-MBE
A thin AlN layer formed by interface reaction epitaxy (IRE-AlN) on a β-Si3N4/Si(111) structure acting as a double buffer layer was used for the growth of GaN or AlN by plasma assisted molecular beam epitaxy (PA-MBE). The β-Si3N4/Si is also grown using IRE with Si and nitrogen atoms supplied by the indirect exposure from an induction coupling plasma discharge of nitrogen gas. The IRE-AlN was formed by a solid state IRE between Al irradiated atoms and N atoms in the β-Si3N4 layer. The thickness of IRE-AlN and β-Si3N4 films was measured by X-ray photoelectron spectroscopy (XPS) and the surface reconstruction structure and morphology was observed using reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM). Surface reconstruction of the β-Si3N4 film with 8x8 and 8/3x8/3 was prepared when the nitridation temperature of Si was at 830 0C and 300 0C with 830 0C anneling, respectively. The intensity of the Al 2p signal increased linearly with increasing nitridation time under Si 7x7 reconstruction. The surface morphology of AlN formed only on the edge of the step when nitridation was performed on a Si(111) 1x1 surface, whereas AlN was formed on the terrace when nitridation was performed on a 7x7 surface. Al polarity AlN was grown on the 8x8 reconstruction of β-Si3N4 and N polarity AlN was grown on a 8/3x8/3 site. The polarity of successive growth of GaN on the double butter layer of AlN/β-Si3N44/Si was the same polarity as the buffer layer. The surface morphology of Ga polarity GaN showed 3D islands when compared with N polarity GaN, because Ga atoms easily incorporate with the (0001) face rather than the (10-11) face on the surface of Ga polarity GaN

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2009 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by rf-discharge! (II)

2009 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by rf-discharge! (II)

Indirect exposure of nitrogen (N) atoms to a surface of Si(111) substrate was realized by adsorbed (ADS) N atoms, which were in a state of local equilibrium. The ADS flux was measured by a parallel plates electrode (atom probe), which was biased negatively by the self ionization of N atoms on negatively the biased electrode. The power and pressure dependences of inductively coupled rf discharge for direct and indirect N fluxes from the rf discharge tube were measured by the atom probe. The surface steps on Si(111) were controlled by the decomposition of an SiO2 layer and phase transformation from 1x1 to 7x7 surface reconstruction states of Si(111). The ADS N atoms reacted with Si and formed β-Si3N4 by interface reaction epitaxy (IRE). The surface morphology of β-Si3N4 was affected by the nitridation temperature and time. Flat β-Si3N4 surfaces on Si(111) were obtained by successive IPE of AlN with Al and N in the β-Si3N4.

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2008 report (2) (in Japanese)
Reaction growth of AlN template on Si for group III nitrides using RF-MBE by interfacial reaction of Al and β-Si3N4

2008 report (2) (in Japanese)
Reaction growth of AlN template on Si for group III nitrides using RF-MBE by interfacial reaction of Al and β-Si3N4

The structure and density of AlN, which was formed by the reaction between N atom in β-Si3N4 and deposited Al atoms, were controlled by the surface morphology of β-Si3N4. β-Si3N4 was fabricated by the nitridation of Si using N+N* or N2* generated by RF discharge. AlN films grown on β-Si3N4/Si have the relationship of AlN(0001)//β-Si3N4(0001)//Si(111) and AlN<11-20>// Si<-110>, which is confirmed by RHEED pattern. The structure of AlN islands was affected by the condition of nitridation such as kind of nitrogen species, nitridation time and surface reconstruction of Si. After the Al deposition and the successive solid state reaction, small islands of AlN were formed on β-Si3N4 formed by N+N*flux, whereas triangular islands were found on β-Si3N4 by N2* flux. In addition, the size and density of AlN islands were affected by the Si surface reconstruction structures under the nitridation condition.

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2008 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by RF-discharge

2008 report (1) (in Japanese)
Measurement of nitrogen atom flux and growth of β-Si3N4 on Si(111) by RF-discharge

Atom nitrogen flux created by the inductive coupling rf discharge was measured by the self ionization of N atoms on negatively biased electrode. The reaction between N atom of the Surface reaction of Si and N atoms produces β-Si3N4. The number of steps was controlled by the thickness of SiO2 layer. The surface morphology of β-Si3N4 was affected by the kind of nitrogen species. When only (N+N*) were used for nitridation in the condition of flux 0.02ML/s, it was found that several island structures which were detached from upper terrace were formed. The island size of β-Si3N4 became bigger without detachment from upper terrace when N2* were used.

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2007 report (in Japanese)
Heteroepitaxial growth of AlN and GaN on Si substrates by RF-MBE using activity modulation migration enhanced epitaxy

2007 report (in Japanese)
Heteroepitaxial growth of AlN and GaN on Si substrates by RF-MBE using activity modulation migration enhanced epitaxy

Induction coupling (ICP) radio-frequency discharge, which has two discharge modes of low brightness (LB) discharge modes
under electrostatic E mode and high brightness (HB) discharge under electromagnetic H mode, is investigated for the RF-MBE growth of group III nitrides. Only excited nitrogen molecules (N2*) , which are chemically inactive and physically active, were formed under the LB discharge. Ground and excited nitrogen atoms (N+N*) , which are chemically active, were dissociated from the excited nitrogen molecules under the HB discharge. The chemical state of (N+N*) atoms is very active compared with that of N2*. On the other hand the physical state of N2* is active to transfer their energy to Ga or Al atoms for enhancement of migration. The exposure of the excited N2* is equivalent of keeping a substrate at higher temperature. Role of these active nitrogen species was studied on the nitridation of Si(111) surface. Excitation of Ga adatoms by the exposure of the excited N2* molecules was confirmed by the combinatrial growth of GaN. Alternating excitation of the LB and HB discharges is called as an activity modulation migration enhanced epitaxial (AM-MEE) growth method. The AM-MEE is useful to grow films of GaN, AlN and their alloys. Control of the polarity of 2H-AlN was successful to putting 1.8 ML(monolayer) of Al before the AM-MEE growth for the Al polarity. HVPE ( Hydride vapor phase epitaxy) growth of 2H-AlN using the template of Al polarity of AlN on Si. An atomic probe for nitrogen atom detection is also fabricated and demonstrated.

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2006 report (in Japanese)
Crystal growth and characterization for a nano-hetero-interface of quantum well structure formed by group III nitride semiconductors on silicon substrates

2006 report (in Japanese)
Crystal growth and characterization for a nano-hetero-interface of quantum well structure formed by group III nitride semiconductors on silicon substrates

For the first year report of this project the aim of the research and results are presented. In order to grow high quality hexagonal GaN on Si substrates the production of atomic nitrogen using two discharge modes of the induction coupling (ICP) discharge was investigated. Using the two ICP discharge modes a new mode-change migration enhanced epitaxial (MC-MEE) growth method was developed. The MC-MEE uses the discharge mode change between low bright (LB) discharge (the excitation of N2 molecules) and high bright (HB) one (the dissociation of N2 molecules to N atoms). As an intermediate layer between Si and GaN a template 2H-AlN was formed by formation of γ phase of Al on Si and the nitridation of Si surface before the AlN template growth using MC-MEE. The sequence of the LB and HB nitrogen flux irradiation was effective to control of active nitrogen species for growth of GaN and AlN. The control of activated nitrogen flux against Ga or Al flux was found to be essential for the growth of high quality
crystal of 2H-GaN and 2H-AlN epitaxial films. Growth of 2H-GaN on Si(111) was confirmed in situ using reflection high energy
electron diffraction.

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Published academic papers

2013 : P hys. Status Solidi C 10, No. 3, 429?432 (2013)
Tadashi Ohachi, Yuka Yamamoto, Osamu Ariyada, Yuuki Sato, Sinzo Yoshikado, and Motoi Wada

2013 : P hys. Status Solidi C 10, No. 3, 429?432 (2013)
Tadashi Ohachi, Yuka Yamamoto, Osamu Ariyada, Yuuki Sato, Sinzo Yoshikado, and Motoi Wada

Activity modulation MEE growth of group III nitrides on Si(111) using PA-MBE

As a demonstration of the activity modulation migration enhanced epitaxy (AM-MEE) heteroepitaxial 2H-AlN thin films of 53.8 nm and 171.3 nm thickness on Si(111) on a double buffer layer (DBL) have been grown by the AM-MEE of plasma assisted molecular beam epitaxy (PA-MBE) method. It is a droplet free growth and an atomic layer epitaxy (ALE). The influence of the DBL, which was formed in a MBE chamber before the AM-MEE growth of 2H-AlN thin films on Si(111), was studied to improve the crystallinity of AlN films. For the growth of high quality 2H-AlN on Si(111), the optimization of growth of the DBL. The interface roughness of the DBL as a layer between two layers of AlN and Si, AlN/DBL/Si was characterized by grazing incidence Xray reflectivity (GIXR) and the surfaces were observed by AFM. Full width at half maximum (FWHM) of ω /2θ for 53.8 nm and 171.3 nm thickness AlN (0002) films were 12.1 arcmin and 7.1 arcmin, respectively. AFM images showed droplet free growth after the AM-MEE and importance of the preparation of initial clean Si surface. Unifrom formation of DBL on a large size wafer of Si was available to use indirect exposure of N radical atoms. By increasing the thickness of the AlN the crystallinity was improved but the surface roughness of AlN did not depend on the thickness of the AlN films obtained by fitting results of GIXR curves.

2011: P hys. Status Solidi C 8, No. 5, 1552?1555 (2011)
Epitaxial growth of β-Si3N4 by the nitridation of Si with adsorbed N atoms for interface reaction epitaxy of double buffer AlN(0001)/ β-Si3N4/Si(111)

2011: P hys. Status Solidi C 8, No. 5, 1552?1555 (2011)
Epitaxial growth of β-Si3N4 by the nitridation of Si with adsorbed N atoms for interface reaction epitaxy of double buffer AlN(0001)/ β-Si3N4/Si(111)

A fabrication process of an interface reaction epitaxy (IRE) β-Si3N4 and an IRE AlN were investigated to produce a double buffer layer (DBL) of AlN(0001)/β- Si3N4/Si(111) for the growth of group III nitrides films on Si. The β-Si3N4 was formed by using adsorbed (ADS) nitrogen atoms irradiated indirectly from a rf-plasma cell. Two surface structures of the β-Si3N4, which were “8 x 8” and “8/3 x 8/3” reconstructions, were fabricated by changing the nitrogen irradiation conditions; complete and incomplete nitridation of Si surface and successive heat treatment up to 875 oC formed the “8 x 8” and “8/3 x 8/3” structures, respectively. IRE AlN was grown by 1 monolayer of Al deposition on the β-Si3N4 and successive annealing at 875 oC. Al and N polarity DBLs were grown on the “8 x 8” and “8/3 x 8/3” structures, respectively. These results indicated that the polarity of DBL could be controlled by the surface reconstruction of β-Si3N4.

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2011: P hys. Status Solidi C 8, No. 5, 1491?1494 (2011)
In situ measurement of adsorbed nitrogen atoms for PA-MBE growth of group III nitrides on Si

2011: P hys. Status Solidi C 8, No. 5, 1491?1494 (2011)
In situ measurement of adsorbed nitrogen atoms for PA-MBE growth of group III nitrides on Si

An atom probe of two parallel electrodes is proposed to monitor adsorbed (ADS) nitrogen atoms in situ during growth of β- Si3N4 using indirect exposure of effusing active nitrogen beam from the radio frequency induction coupled plasma cell. The β- Si3N4 film is a component of a double buffer layer (DBL) AlN(0001)/β-Si3N4/Si(111) to grow high quality the group III nitrides and their alloys on Si. Atom current between the parallel electrodes corresponds to flux of the ADS nitrogen atoms on the inside surface at the atom potential, VA. The ADS atom current received influence of wall and shutter of the cell, because adsorption of nitrogen atom depended wall condition such as temperature and the concentration of adatoms on the wall.

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2011: Journal of Crystal Growth 318 (2011) 474?478
Interface roughness of double buffer layer of GaN film grown on Si(111) substrate using GIXR analysis

2011: Journal of Crystal Growth 318 (2011) 474?478
Interface roughness of double buffer layer of GaN film grown on Si(111) substrate using GIXR analysis

A double buffer layer (DBL), interface reaction epitaxy (IRE) AlN/b-Si3N4/Si, grown by an IRE of b-Si3N4 and AlN films on Si, was fabricated to improve the crystalline quality of successively grown 30 nm GaN on a 30 nm AlN buffer layer using plasma-assisted molecular beam epitaxy (PA-MBE). The DBL was first prepared by surface nitridation of Si and successively prepared by IRE between the deposited Al and N atoms in b-Si3N4. Both the AlN buffer layer on the DBL and GaN filmon the AlN buffer layer were grown by activity-modulation migration enhanced epitaxy (AM-MEE). Hetero epitaxial grown films of GaN(30 nm)/AlN buffer(30 nm)/DBL/Si(1 1 1) were prepared for analysis using a three layer model of grazing incidence-angle X-ray reflectivity (GIXR), which consisted of three layers of GaN, AlN buffer and Si and of the three interfaces of the GaN surface, GaN/AlN buffer and AlN buffer/DBL/Si. The nitridation temperature dependence of the interface roughness of the DBL was measured to be 0.5 and 0.6 nm, for nitridation temperatures of 780 and 830 1C, respectively. The full width at halfmaximum (FWHM) of rocking curve GaN(0 0 0 2) measured by X-ray diffraction (XRD) for nitridation temperatures of 780 and 830 1C were 58.2 and 55.2 arcmin, respectively.

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2011: Journal of Crystal Growth 318 (2011) 468?473
Control of active nitrogen species used for PA-MBE growth of group III nitrides on Si

2011: Journal of Crystal Growth 318 (2011) 468?473
Control of active nitrogen species used for PA-MBE growth of group III nitrides on Si

A new spiral parallel mesh electrode (PME) is presented to control active nitrogen species in plasmaassisted molecular beam epitaxial (PA-MBE) growth of group III nitrides and their alloys. Direct flux of active nitrogen from radio frequency inductive coupled plasma (rf-ICP) discharge was able to be measured using a mesh electrode for filtering charge particles and electron emission due to the selfionization of nitrogen atoms on a negatively biased electrode. In situ measurement of direct nitrogen atom fluxes using the spiralPME during PA-MBE growth of GaN and AlN on Si substrates is investigated. A linear rf power dependence of direct flux of active species on atoms such as nitrogen (N+Nn), where N and Nn were ground and excited atoms, respectively, from a rf-ICP was confirmed by the spiral PME. An indirect flux of nitrogen adsorbed (ADS) atoms (N+Nn) during discharge was also monitored by the spiral PME and received influence of the wall surface of the growth chamber. ADS nitrogen atoms are able to be used for nitridation of Si surface to grow a double buffer layer (DBL) AlN/b-Si3N4/Si.

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2011: Japanese Journal of Applied Physics 50 (2011) 01AE01
Improvement of Plasma-Assisted Molecular Beam Epitaxial Growth of Group III Nitrides on Si Controlling Radio Frequency Discharge Modes and Irradiation of Nitrogen Flux

2011: Japanese Journal of Applied Physics 50 (2011) 01AE01
Improvement of Plasma-Assisted Molecular Beam Epitaxial Growth of Group III Nitrides on Si Controlling Radio Frequency Discharge Modes and Irradiation of Nitrogen Flux

A radio frequency inductively coupled plasma (rf-ICP) nitrogen discharge was investigated to improve group III nitride growth on Si substrates. Two modes of the rf-ICP discharge, low brightness (LB) and high brightness (HB) discharges, were successfully controlled through mode transition. Direct irradiation and indirect irradiation of nitrogen atoms were applied for the growth of group III nitrides. As an application of indirect irradiation of nitrogen atoms, the growth of _-Si3N4 using interface reaction epitaxy (IRE) was studied. As applications of direct irradiation of nitrogen atoms, activity modulation migration-enhanced epitaxy (AM-MEE) and plasma-assisted molecular beam epitaxy (PA-MBE), which are atomic layer epitaxy (ALE) methods, are demonstrated. These growth systems operate to realize a single-growth process from a Si substrate to an AlN or GaN epitaxial layer, i.e., through preparation of a double buffer (DBL) layer of AlN/_-Si3N4/Si after the growth of IRE _-Si3N4 and IRE AlN. The electron emission due to the self-ionization of nitrogen atoms on a negatively biased electrode is demonstrated to measure in situ direct and indirect nitrogen atom fluxes during the growth. # 2011 The Japan Society of Applied Physics

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2009: Journal of Crystal Growth 311 (2009) 2987?2991
Measurement of nitrogen atomic flux for RF-MBE growth of GaN and AlN on Si substrates

2009: Journal of Crystal Growth 311 (2009) 2987?2991
Measurement of nitrogen atomic flux for RF-MBE growth of GaN and AlN on Si substrates

Production and measurement of active nitrogen atoms (N+N*), which consist of ground state nitrogen atoms N and excited state nitrogen atoms N*, in an inductively coupled radio frequency discharge for the growth of group III nitrides and their alloys using a molecular beam epitaxy (MBE) were studied. Two discharge modes of the low brightness (LB) and the high brightness (HB) used in this study to produce excited nitrogen molecules (N2*) and dissociated active nitrogen atoms (N+N*). The flux of (N+N*) was measured by a Langumuir-like electrode due to the self-ionization of adsorbed (N+N*) on a negatively biased electrode. The self-ionization, which emits electrons from (N+N*), forms an atom current and is confirmed using different electrodes such as Pt and CuBe and different electrode area. The atom current was calibrated by the grown GaN thickness in a VG80H MBE machine. The calibrated flux of (N+N*) per atom current in the VG80H machine is 5.5_10_4ML/s/nA, where ML is monolayer. The atom current is useful to monitor the flux of chemically active nitrogen atoms N+N* for growth of group III nitrides and their alloys. Activity modulation migration enhanced epitaxial growth (AM-MEE) was demonstrated as an application of the measurement of atom current for the growth of the group III nitrides.

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2009: Journal of Crystal Growth 311 (2009)
Nitridation of Si(111) for growth of 2H-AlN(0 0 01)/b-Si3N4 /Si(111) structure

2009: Journal of Crystal Growth 311 (2009)
Nitridation of Si(111) for growth of 2H-AlN(0 0 01)/b-Si3N4 /Si(111) structure

Using various nitrogen active species with different chemical and physical activities, nitridation of Si(111) was studied for the growth of group III nitrides and their alloys using a radio frequency molecular beam epitaxy. Nitrogen inductive coupling discharge produced dissociated active nitrogen atoms (N+N*), which are ground state atom N and excited atom N*, excited molecules N!2, and molecule ions N2 + . The surface morphology of b-Si3N4 was affected by the kind of nitrogen species. Flat surface was obtained by using only (N+N*) with slow nitridation of 0.02 ML/s. When nitridation was performed by (N+N*) and N!2, many steps and many 10nm height spikes were observed. It was essential for nitridation to eliminate nitrogen ions (N2 + ). In comparison with this result, when N!2 were used, the island size of b-Si3N4 became bigger without detachment from upper terrace. This island size affected successive surface structure of AlN. It is a key technique to achieve flat surface of b-Si3N4 that N+N* flux was used for nitridation. The growth of 2H-AlN(0 0 01)/b-Si3N4/Si(111) structure was also performed. RMS value of AlN grown on b-Si3N4 which was formed by (N+N*) became 0.88 nm.

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2006: phys. stat. sol. (c) 3, No. 6, 1404?1407 (2006)
Radio-frequency MBE growth of cubic GaN on 3C-SiC(001)/Si(001) template

2006: phys. stat. sol. (c) 3, No. 6, 1404?1407 (2006)
Radio-frequency MBE growth of cubic GaN on 3C-SiC(001)/Si(001) template

A 3C-SiC(001) was formed by coincidence site lattice matching on Si(001) through carbonization using acetylene (C2H2) supplied by a jet nozzle. The 3C-SiC serves as a cubic template for the MBE growth of c-GaN on Si substrates. The Si substrate with lattice constant of aSi = 0.544 nm was covered with strained 3C-SiC whose lattice constant a3C-SiC/Si = 0.445 nm expanded from that of the bulk 3C-SiC crystal (0.438 nm). Better quality cubic phase GaN film was grown on the strained 3C-SiC template layer when the Ga/N flux ratio approached unity of Ga rich side. The proportion of the cubic phase in the GaN layer was calculated to be 94.7% from the integrated intensity ratio of the X-ray diffraction peaks of c-GaN(002) and h-GaN(10-11). The FWHM of the (002) diffraction peak for the 544 nm-thick c-GaN was 13.2 arcmin. A precise RHEED analysis also indicated that the c-GaN had (2x2) surface reconstruction structure.

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2006: phys. stat. sol. (c) 3, No. 6, 1383?1387 (2006)
Radio-frequency MBE growth of cubic GaN on BP(001)/Si(001) hetero-structure

2006: phys. stat. sol. (c) 3, No. 6, 1383?1387 (2006)
Radio-frequency MBE growth of cubic GaN on BP(001)/Si(001) hetero-structure

Zincblende gallium nitride (c-GaN) was grown on zincblende boron monophosphide (BP)/silicon (001) using radio-frequency plasma-assisted molecular-beam epitaxy (RF-MBE). In spite of near perfect latticematch coordination between c-GaN and BP, the initial nucleation of c-GaN was 3D island formation due to imperfect wetting. Using cross-sectional electron backscatter diffraction pattern (x-EBSD), it was found that dislocations were eliminated with an increase of epilayer thickness of c-GaN, and finally 99.4% c-GaN (001) was achieved. The (2x2) and (4x1) reconstructions of the surface of almost pure c- GaN (001) were confirmed by reflection high-energy electron diffraction (RHEED) under arseniccontamination free conditions.

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2006: Journal of Crystal Growth 292 (2006) 221?226
Role of excited nitrogen species in the growth of GaN by RF–MBE

2006: Journal of Crystal Growth 292 (2006) 221?226
Role of excited nitrogen species in the growth of GaN by RF–MBE

Optical emission spectroscopy (OES) was used with the combinatorial growth method to investigate the behavior of excited nitrogen species in the growth of gallium nitride (GaN) using radio-frequency molecular beam epitaxy (RF?MBE). To determine the amounts of each excited nitrogen species in the nitrogen plasma, the integrated OES intensity (IOI) method was proposed. The IOI measurements revealed the following: more nitrogen ions .N.2 . were produced at the lower inlet pressure of nitrogen, the productivity of nitrogen atoms (N) and excited nitrogen atoms (N*) had an optimum value at some inlet pressure, whereas the productivity of excited nitrogen molecules .N$2 . saturated as the inlet pressure increased. The combination of the IOI measurement and the combinatorial growth of GaN showed that not only N and N*, but also the long-lifetime A3S.u state of N$2 contributed to GaN growth using RF?MBE.

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2006: J. Rare Earths, 24 (2006)1.
Growth of GaN/AlxGa1-xN (x=0.65) superlattices on Si(111) substrates using RF-MBE

2006: J. Rare Earths, 24 (2006)1.
Growth of GaN/AlxGa1-xN (x=0.65) superlattices on Si(111) substrates using RF-MBE

Superlattices with varying GaN well widths (2, 3, 6, 9 nm) and fixed AlGaN barrier (8nm) with high Al-content (x=0.65) were grown. Streaky RHEED patterns indicated 2D growth mode for the superlattices. XRD measurements showed multiple satellite peaks corresponding to uniform periodicity of the GaN/AlGaN pairs. The AlGaN barrier XRD peak also shifted with increasing well widths, while the GaN XRD peak was nominally unchanged. Room temperature photoluminescence experiments revealed peak emissions at energies lower than the bulk GaN energy gap. The large red shift with respect to the bulk gap is attributed to significant Stark effect for wide multiple quantum wells.

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2005: Journal of Crystal Growth 275 (2005) e1215?e1221
3C-SiC/Si template growth and atomic layer epitaxy of cubic GaN by RF-MBE

2005: Journal of Crystal Growth 275 (2005) e1215?e1221
3C-SiC/Si template growth and atomic layer epitaxy of cubic GaN by RF-MBE

Growth of 2 in cubic gallium nitride (c-GaN) film on a cubic silicon carbide on Si template (3C-SiC/Si) using Si (0 0 1) and Si(1 1 1) substrates was performed by usinga radio frequency molecular beam epitaxy (RF-MBE) system, which was equipped with a jet nozzle. The 3C-SiC/Si template was prepared usingalternatingexposure of acetylene .C2H2. gas introduced by the jet nozzle under ultra high vacuum and Si molecular beam from a Si effusion cell. Very smooth 3C-SiC/Si templates with RMS roughness by atomic force microscopy of about 0.2?0.4nm were grown here. Good crystal quality of low-temperature buffer (LTB) layer was obtained on a good 3C-SiC/Si template and confirmed through the observation of RHEED pattern. A grown c-GaN film’s X-ray diffraction full-width at half-maximum of (0 0 2) peak was 13.2 arcmin (2y) for a 544 nm-thick film. c-GaN was also grown using an atomic layer epitaxy (ALE) method. The ALE method proved to be necessary for a uniform and homogeneous atomic nitrogen flux under slightly Ga excess condition to grow the uniform c-GaN using rf-MBE.

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2005: Journal of Crystal Growth 275 (2005) e1197?e1202
Control of nitrogen flux for growth of cubic GaNon 3C-SiC/Si by RF-MBE

2005: Journal of Crystal Growth 275 (2005) e1197?e1202
Control of nitrogen flux for growth of cubic GaNon 3C-SiC/Si by RF-MBE

The enhancement of the production rate of nitrogen radical from a radio frequency (RF) discharge plasma is reported through the application of a DC magnetic field under RF-ECR (electron cyclotron resonance of RF) condition. High efficiency of the nitrogen radical production was realized by an optimum magnetic field for the resonance of about 0.5mT for the electron energy of 2 eV for the 13.56-MHz discharge. The effect of controlling the divergence of the nitrogen radical flux by changing the orifice dimension was studied by measuring the color change of interference due to the film thickness. The aspect ratio of the orifice hole and the distribution of hole position determined the flux diversity. Combinatorial methodology, which realizes various III/V flux ratio without substrate rotation due to non-uniform flux, was used to study the effect of the III/V flux ratio to poly-type formation by photoluminescence. The cubic phase was grown under a stoichiometric condition of slightly Ga-rich side, with an III/V ratio of about one.

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2003: phys. stat. sol. (c) 0, No. 7, 2589?2592 (2003)
Direct growth of cubic AlN and GaN on Si (001) with plasma-assisted MBE

2003: phys. stat. sol. (c) 0, No. 7, 2589?2592 (2003)
Direct growth of cubic AlN and GaN on Si (001) with plasma-assisted MBE

Highly lattice mismatched (HM2) heteroepitaxial growth of cubic zincblende c-AlN and c-GaN on Si(001) was performed by MBE using plasma excited nitrogen sources without using a low temperature buffer layer. The early stage of the direct nucleation of AlN and GaN on a Si substrate using microwave and radio frequency plasma-assisted MBE was studied. The islands of a zincblende structured material (c-SiNx [a = 0.43 nm]), effectively worked as a seed for successive coherent growth of c-AlN and c-GaN oriented 〈001〉. The growth of c-AlN and c-GaN was analyzed by reflection high energy electron diffraction, X-ray diffraction, and photoluminescence.

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