成果報告書詳細
管理番号20130000000831
タイトル*平成23年度中間年報 省エネルギー革新技術開発事業 超高耐圧酸化ガリウムパワーデバイスの研究開発(H23-H25)
公開日2013/10/22
報告書年度2011 - 2011
委託先名国立大学法人京都大学 国立大学法人東京工業大学 独立行政法人情報通信研究機構 株式会社タムラ製作所 株式会社光波
プロジェクト番号P09015
部署名省エネルギー部
和文要約
英文要約Title:Research and Development Program for Innovative Energy and Efficiency Technology. Research and Development of Ultra-High-Voltage Gallium Oxide Power Devices (FY2011-FY2013) FY2011 Annual Report

1-1) Beta-Ga2O3 bulk crystals were prepared by the FZ and EFG methods. N-type Ga2O3 films were homoepitaxially grown by ozone MBE. The growth rate was increased by more than ten times by changing from the (100) to (010) plane. The carrier concentration of the epitaxial layers was varied over 1016-1019 cm-3 by changing the Sn doping concentration. Pt SBDs on 1.4-micron-thick Ga2O3 homoepitaxial layers exhibited a reverse breakdown voltage of 100 V, an on-resistance of 0.002 ohm-cm2, and a forward voltage of 1.7 V (at 200 A/cm2).
1-2) Using a Sn-doped Ga2O3 layer grown on a semi-insulating beta-Ga2O3 (010) substrate, we fabricated a circular MESFET with a gate length of 4 micron and a source-drain spacing of 20 micron. The device showed an ideal transistor action represented by the drain current modulation due to the gate voltage (VGS) swing. A complete drain current pinch-off characteristic was also obtained for VGS < -20 V, and the three-terminal off-state breakdown voltage was over 250 V. A low drain leakage current of 0.003 mA at the off-state led to a high on/off drain current ratio of about 10000.
2-1-1) A mist CVD method allows corundum-structured alpha-Ga2O3 on sapphire, which can complement beta-Ga2O3 devices by forming various corundum-structured heterojunctions. Cross sectional TEM revealed defect confinement at the interface, suppressing propagation of dislocations into the epilayers. Sn-doping achieved n-type conduction with the carrier concentration of 1019 cm-3. We showed alpha-(AlxGa1-x)2O3 thin films of x and the band gap upto 0.81 and 7.4 eV, respectively, and alpha-(AlxGa1-x)2O3/Ga2O3 heterointerface without noticeable interface defects.
2-2-1) Beta-Ga2O3(101) homoepitaxial films were grown by PLD. Atomically flat surface with step and terrace structures was obtained, which has enough crystalline quality for the following research of carrier concentration control by impurity doping using combinatorial approach.
2-2-2) (AlxGa1-x)2O3 alloy films were grown on c-plane sapphire substrates by PLD. With increasing x, the alloy films show wider band gaps. This implies that the applications of Ga2O3 are not limited to the homo-junction devices, but can be expanded to hetero-junctions devices.
2-4) SBDs fabricated using beta-Ga2O3 substrates with donor concentrations of 3 or 5x1016cm-3 exhibited nearly-ideal I-V characteristics with the ideality factor of 1.04-1.06.
2-5) With the EFG method, improvements of growth equipment and conditions resulted in forming the 48-mm-wide twin-defect-free region in 2-inch-width bulk beta-Ga2O3 crystals. This was almost four times wider compared to our previous achievements and may direct us to the successful formation of twin-defect-free crystals markedly in advance of the planned date.
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