2004 Fiscal Year Final Research Report Summary
Surface/interface control of high-frequency and high-power transistors based on GaN materials
| Project/Area Number |
14350155
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Electronic materials/Electric materials
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| Research Institution | HOKKAIDO UNIVERSITY |
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Principal Investigator |
HASHIZUME Tamotsu Hokkaido Univ., Res.Center for Integrated Quantum Electronics, Prof., 量子集積エレクトロニクス研究センター, 教授 (80149898)
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| Co-Investigator(Kenkyū-buntansha) |
MOTOHISA Junichi Hokkaido Univ., Res.Center for Integrated Quantum Electronics, Ass.Prof., 量子集積エレクトロニクス研究センター, 助教授 (60212263)
KASAI Seiya Hokkaido Univ., Grad.School of Info.and Sci., Ass.Prof., 大学院・情報科学研究科, 助教授 (30312383)
AKAZAWA Masamichi Hokkaido Univ., Res.Center for Integrated Quantum Electronics, Ass.Prof., 量子集積エレクトロニクス研究センター, 助教授 (30212400)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Gallium Nitride / surface control / interface control / Schottky contact / heterointerface / Fermi level pinning / Al_2O_3 / HFET |
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| Research Abstract |
The purpose of this research was to characterize and control surface/interface properties of GaN-based material systems such as AlGaN/GaN hetrostrcutures for the stability improvement of high-frequency and high-power transistors. The main results obtained are listed below :
(1)Serious deterioration such as stoichiometry disorder and nitrogen deficiency (N deficiency) was found at the processed AlGaN surfaces. This resulted in formation of a localized deep donor level related to N vacancy (V_N), causing excess leakage currents at the AlGaN Schottky interface and serious drain current collapse in AlGaN/GaN heterostructure field effect transistors.
(2)An Al_2O_3-based surface passivation scheme including the N_2-plasma surface treatment was proposed and applied to an insulated-gate type HFET. A large conduction-band offset of 2.1 eV was achieved at the Al_2O_3/Al_<0.3>Ga_<0.7>N interface. No current collapse was observed in the fabricated Al_2O_3 insulated-gate HFETs under both drain stress and gate stress.
(3)From the detailed temperature-dependent current-voltage (I-V-T) measurements, we discussed the mechanism of leakage currents through GaN and AlGaN Schottky interfaces. The experiments were compared to the calculations based on thin surface barrier model in which the effects of surface defects were taken into account. Our simulation results indicates that the barrier thinning caused by unintentional surface-defect donors enhances the funneling transport processes, leading to large leakage currents through GaN and AlGaN Schottky interfaces.
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Research Products
(36 results)
