2001 Fiscal Year Final Research Report Summary
"Insulated gate structures on GaN and their interface properties"
| Project/Area Number |
11650309
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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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, Ass. Pro., 量子集積エレクトロニクス研究センター, 助教授 (80149898)
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| Co-Investigator(Kenkyū-buntansha) |
TAKEYAMA Mayumi Kitami Inst. Technol., Ass. Pro., 工学部, 助教授 (80236512)
KANESHIRO Chinami Kanagawa Inst. Technol., Faculty of Eng., Inst., 工学部, 助手 (30318993)
MOTOHISA Junichi Hokkaido Univ., Res. Center for Integrated Quantum Electronics, Ass. Pro., 量子集積エレクトロニクス研究センター, 助教授 (60212263)
FUJIKURA Hajime Hitachi Cable LTD., Senior Researcher, 主任研究員(研究職)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Gallium Nitride / surface control / interface control / MIS structure / surface treatment / Fermi level pinning / SiN_χ / Al_2O_3 |
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| Research Abstract |
For the application to high-power/high-frequency electronic devices, we have investigated the formation processes of insulated structures on GaN and their interface properties. The main results obtained are listed below :
(1) Chemistry and electronic properties of GaN surfaces after various kinds of surface treatments were characterized by x-ray photoelectron spectroscopy (XPS). Strong upward band bending of 1.4 eV was found at the air-exposed GaN surface. This is due to the high density of surface states. The surface treatment in the NH_40H solution and the ECR-excited N_2 plasma significantly decreased the surface band bending to 0.5 eV, indicating the reduction of the Fermi level pinning.
(2) We have successfully fabricated the SiN_χ gate structure on the treated n-GaN surface by the ECR-CVD process. The SiN_χ/n-GaN structure showed the type-I band lineup and a low interface state density distribution in the range of 10^<11> cm^<-2> eV^<-1>. The surface passivation utilizing the ECR-C
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VD SiNx film enhanced the drain saturation current and improved the stability in the GaN/AlGaN heterostructure field effect transistors.
(3) Electrical characterization of AlN/GaN interfaces was carried out by the C-V technique in samples grown by metal organic chemical vapor deposition. A low value of interface state density D_<it> of < 1x 10^<11> cm^<-2> eV^<-1> was achieved around the energy position of Ec-0.8eV. This indicates that the AlN/GaN structures have good interface properties with low interface state density, and are very promising for advanced MIS devices.
(3) A novel surface passivation process for AIGaN/GaN heterostructures utilizing an ultrathin Al_20_3 layer (〜1 nm) was proposed. The reverse leakage current for the Schottky gate contact on the Al_20_3-passivated heterostructure surface was reduced by three orders of magnitude than that for the conventional Schottky gate structure. C-V results showed good gate controllability of two-dimensional electron gas (2DEG) by the novel gate structure. Less
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