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成果報告書詳細
管理番号20180000000209
タイトル*平成29年度中間年報 エネルギー・環境新技術先導プログラム α型酸化ガリウム高品質自立基板の研究開発
公開日2018/12/27
報告書年度2017 - 2017
委託先名国立研究開発法人物質・材料研究機構 国立大学法人京都大学 国立大学法人佐賀大学 株式会社FLOSFIA
プロジェクト番号P14004
部署名イノベーション推進部
和文要約
英文要約Title: Advanced Research Program for Energy and Environmental Technologies / Development of high-quality freestanding α-Ga2O3 substrates(FY2016-FY2018) FY2017 Annual Report

(1) n-type doping control of α-Ga2O3 by HVPE (A-1)
We will try n-type doping control of α-Ga2O3 using GeCl4 as the source material. The ionic radius of Ge is close to that of Ga, and therefore the crystal quality should be better compared to the case of conventional dopants such as Si or Sn. This fiscal year, we have theoretically investigated how the source temperature and the bubbling rate should be, based on the vapor pressure curve of GeCl4 and our experience in HVPE of Ge-doped GaN. We have decided to employ a new technique in which HCl gas is flown together with GeCl4 in order to improve the doping efficiency and minimize the memory effect. In addition, we have discussed the methodology to optimize the timing of gas feeding, which produces appropriate doping depth profile in the epilayer, taking gas feed rate and the volume of gas piping and reactor tube into account.

(2) Growth study of high-quality α-Ga2O3 layers using super lattice buffer layers / ELO by mist CVD (B-1)
We have been investigated the layer structure design of mist-CVD-grown -Ga2O3 templates, which will be used for the thick film growth by HVPE. We considered the controllability of layer thickness and Al composition of the super lattice structure based on our past results, and concluded that it will be possible to grow super lattice structures with precisions better than 20nm in thickness and Al composition of 5%. We also considered the mask design of ELO based on the possible growth rate of mist-CVD, and concluded that Al2O3 or SiO2 amorphous masks with 10-100 nm thickness and 1-10 μm lateral spacing should work. Furthermore, the combination of super lattice and ELO has also been considered, and the experimental methodology has been established in concrete.

(3) Investigation of defects of α-Ga2O3 crystals (C-1)
The purpose of this study is to identify crystal defects of α-Ga2O3. This fiscal year we investigated mist-CVD grown α-Ga2O3 epilayers by X-ray diffraction. We found that the crystal quality was uniform on the entire crystal and that distribution of the tilt component was very narrow, but the distribution of the twist component was still wide.

(4) Development of CMP process of α-Ga2O3 (D-1)
We have determined the basic strategy of the development to obtain epi-ready surface. We will study the quality of the processed surface from both chemical and physical viewpoints, and clarify the impact of the surface quality on the crystal quality of the re-grown epilayers. α-Ga2O3 epilayers grown on sapphire substrates will be used for the study at the initial stage to conduct the research efficiently.
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