記述言語：英語   出版者・発行元：Vacuum  

Gallium nitride (GaN) films have been grown on GaN/Si templates at a low temperature using our newly developed Radical Enhanced Metal Organic Chemical Vapor Deposition (REMOCVD) system. This REMOCVD system has three features; (1) the application of Very High-Frequency (VHF) of 100 MHz to increase the plasma density; (2) the introduction of H<inf>2</inf> gas together with N<inf>2</inf> gas in the plasma discharge region to generate active NH<inf>x</inf> radical species in addition to nitrogen radicals; and (3) the radical supply under remote plasma arrangement to suppress charged ions and photons by employing a Faraday's cage. It was found that GaN can be grown using this novel REMOCVD technique, even at a low temperature of 800 °C. The crystal quality measured by XRC (X-ray rocking curve)-FWHM (full width half maximum) was very close to that of GaN/Si templates. In the present work, we have modified the TMG supply nozzle with water cooling to prevent TMG to be decomposed inside the nozzle and optimized the growth conditions such as the RF plasma power and the N<inf>2</inf>:H<inf>2</inf> gas ratio and evaluated the XRC-FWHM of grown GaN. It was found that GaN can be grown with the crystal quality better than that of GaN/Si templates, from 1175 arcsec up to about 886 arcsec for GaN (0002) out-plane diffraction and from 2354 arcsec up to 1705 arcsec for GaN (11-20) in-plane diffraction. To the authors' knowledge, this may be the first time that the crystal quality of epitaxial layers was improved better than that of GaN/Si templates.

DOI： 10.1016/j.vacuum.2026.115485

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Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

Gallium nitride (GaN) films have been grown on Si (111) substrates with low-temperature GaN as a buffer layer using a newly developed Radical Enhanced Metal Organic Chemical Vapor Deposition (REMOCVD) system. This REMOCVD system has three features; (1) the application of very high-frequency (VHF) of 100 MHz to increase the plasma density, (2) the introduction of H<inf>2</inf> gas together with N<inf>2</inf> gas in the plasma discharge region to generate active NH<inf>x</inf> radical species in addition to nitrogen radicals, and (3) the radical supply under remote plasma arrangement with suppressed charged ions and photons by employing a Faraday‘s cage. Using this new system, we have studied the homoepitaxial growth of GaN. It was found that high-quality crystals can be grown by REMOCVD at temperatures of 800 °C lower than those of MOCVD. However, the buffer layer is necessary for the heteroepitaxial growth of GaN on Si. In the present study, the low-temperature GaN (LT-GaN) grown at 600 °C was used as the buffer layer. The growth conditions such as the effect of N-termination of Si and the effect of thickness of LT-GaN as a buffer layer were optimized. The surface morphology and the cleaved cross-sectional view of GaN grown on Si substrates were studied by scanning electron microscopy (SEM). The crystal quality of GaN grown on Si substrates was evaluated by X-ray diffraction (XRD). The epitaxial growth of GaN on Si (111) substrates was achieved by the REMOCVD method with a growth rate of approximately 0.6 µm/h at a low temperature of 800 ℃. The present REMOCVD system is a very promising method for the growth of GaN on Si at relatively low temperatures without using toxic and costly ammonia gas.

DOI： 10.1016/j.jcrysgro.2025.128089

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記述言語：英語   出版者・発行元：Scientific Reports  

Correction to: Scientific Reportshttps://doi.org/10.1038/s41598-024-61501-9, published online 13 May 2024 The original version of this Article contained an error in the legend of Figures 20 and 21, where an inset was mistakenly included. Figure 20 “GaN on a GaN template under the best conditions with a growth time of 15 min. (a) Surface morphology (inset is the RHEED pattern), (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” now reads, “GaN on a GaN template under the best conditions with a growth time of 15 min. (a) Surface morphology, (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” And Figure 21 “GaN on a bulk GaN substrate under the best conditions with a growth time of 15 min. (a) Surface morphology (inset is the RHEED pattern), (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” now reads, “GaN on a bulk GaN substrate under the best conditions with a growth time of 15 min. (a) Surface morphology, (b) cross-section by SEM and (c) the omega scan of thin and thick GaN. Growth conditions; 800 °C, 600 W, 300 Pa, TMG + 5 °C/H<inf>2</inf> carrier gas 20 sccm.” The original Article has been corrected.

DOI： 10.1038/s41598-024-82619-w

Open Access

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Scientific Reports  

Using our recently developed radical-enhanced metalorganic chemical vapor deposition (REMOCVD) technique, we have grown gallium nitride (GaN) on bulk GaN and GaN on Si templates. Three features make up this system: (1) applying very high-frequency power (60 MHz) to increase the plasma density; (2) introducing H<inf>2</inf> and N<inf>2</inf> gas in the plasma discharge region to produce active NH<inf>x</inf> radical species in addition to nitrogen radicals; and (3) supplying radicals under remote plasma arrangement with a Faraday cage to suppress charged ions and photons. Using this new REMOCVD system, it was found that high-quality crystals can be grown at lower temperatures than that of MOCVD but the disadvantage was that the growth rate was smaller as 0.2–0.8 μm/h than that by MOCVD. In the present work, we have used a pBN inner shield to prevent the deactivation of radicals to increase the growth rate. The growth conditions such as the plasma power, trimethylgallium (TMG) source flow rate, N<inf>2</inf> + H<inf>2</inf> gas mixture flow rate, and the ratio of N<inf>2</inf>/H<inf>2</inf> were optimized and it was found that the growth rate could be increased up to 3.4 μm/h with remarkably high crystalline quality comparable to that of MOCVD. The XRD-FWHM of GaN grown on the GaN/Si template and the bulk GaN substrate were 977 arcsec and 72 arcsec respectively. This work may be very promising to achieve high-power GaN/GaN devices.

DOI： 10.1038/s41598-024-61501-9

Open Access

Web of Science

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PubMed

記述言語：英語   出版者・発行元：Japanese Journal of Applied Physics  

Metal-organic CVD (MOCVD) is a well-established means of epitaxial growth of III-nitrides in terms of production. To overcome the drawbacks of MOCVD, we have developed a radical-enhanced MOVCVD (REMOCVD) technique which is promising to grow group-III nitride materials at lower temperatures without ammonia gas. The gas phase behavior of trimethyl gallium (TMG) and triethyl gallium (TEG) in the chamber is studied with optical emission spectroscopy (OES) and quadrupole mass spectroscopy. From OES results, it is found that the parasitic reactions due to activated Ga and CN could be avoided by introducing hydrogen as a source gas together with nitrogen gas. The TEG is completely decomposed in REMOCVD at 550 °C which is a much lower temperature compared to TMG in a hydrogen atmosphere. Also, it is found that due to the low decomposition temperature of TEG, TEG contaminated the gas line which needs to be cleaned often.

DOI： 10.35848/1347-4065/acfd34

Open Access

Web of Science

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