2001 Fiscal Year Final Research Report Summary
High breakdown voltage and high frequency field-effect transistors on heteroepitaxial diamond film.
| Project/Area Number |
10450127
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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 | Waseda University |
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Principal Investigator |
KAWARADA Hiroshi Waseda University, School of Science and Engineering, Professor, 理工学部, 教授 (90161380)
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| Co-Investigator(Kenkyū-buntansha) |
NAGASAWA Hiroyuki HOYA, R&D Center, Group Reader, グループリーダー
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| Project Period (FY) |
1998 – 2000
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| Keywords | Diamond / H-terminated surface channel / Field-effect transistor / Cut-off frequency / Maximum frequency of oscillation / Breakdown voltage / MESFET / MISFET |
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| Research Abstract |
For the realization of high performance diamond electronic devices such as high power and high frequency transistors, FETs have been fabricated on hydrogen-terminated diamond surface conductive layer. In order to improve the performance of FETs, self-aligned gate fabrication processes which can reduce the gate length and parasitic resistances have been developed. Utilizing self-aligned gate FET fabrication process, 1 μm Cu gate MESFET realizes high transconductance of 110 mS/mm. This value exceeds the transconductance of SiC-FETs and Si-nMOSFETs of equal gate size. High performance diamond MISFETs have been also realized utilizing the same process. CaF_2 insulator which does not generate the high interface states density between hydrogen-terminated diamond is utilized as gate insulator.The highest transconductance of 86 mS/mm is obtained in 1.2 μm gate length. The MISFET shows high channel mobility of more than 250 cm^2/Vs. This value is more than twice higher than that of inversion type SiC MOSFETs. The high channel mobility is explained by the screening effect.
The RF performances of diamond MESFETs and MISFETs are measured for the first time. The cut-off frequency of 2 μm gate MESFET with transconductance of 70 mS/mm shows 2.2 GHz. On the other hand, much higher cut-off frequency of 11 GHz is realized in diamond MISFET with 0.7 μm gate length. This value is 5 times higher than 2 μm gate MESFETs. Utilizing MIS structure which has gate insulator capacitance in series to surface-channel capacitance, the source to gate capacitance is reduced half as much as that of diamond MESFET. This FET also shows highest fmax of 22 GHz and 15 dB of power gain is obtained at 2 GHz.
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