2004 Fiscal Year Final Research Report Summary
Heteroepitaxy in III-nitride semiconductors by means of control of surface structures in atomistic scale.
| Project/Area Number |
14205001
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Applied materials science/Crystal engineering
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| Research Institution | Hokkaido University |
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Principal Investigator |
TANAKA Satoru Hokkaido Univ., Research Institute for Electronic Science, Associate Professor, 電子科学研究所, 助教授 (80281640)
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| Co-Investigator(Kenkyū-buntansha) |
KUMANO Hidekazu Hokkaido Univ., Research Institute for Electronic Science, Assistant Professor, 電子科学研究所, 助手 (70292042)
AOYAGI Yoshinogu Tokyo Inst.Tech., Interdisciplinary Graduate School of Science and Technology, Professor, 大学院・総合理工学研究科, 教授 (70087469)
SAKAGUCHI Harunori Hitachi Cable, Advanced Research Center, Head, アドバンスリサーチセンタ, センタ長
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| Project Period (FY) |
2002 – 2004
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| Keywords | III-V Nitride / Structural defets / Dislocation / Surface structure / Heteropitaxy / Growth mode / Optical device / Selforganization |
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| Research Abstract |
Reduction of defect density (especially threading dislocations) in group III-nitride thin films is of great importance to achieve high performance optical and electrical devise. Due to the lack of bulk GaN substrate it is obliged to use foreign materials as a substrate, e.g.sapphire and SiC, and thus growth of III-nitrides is done by a heteroepitaxy. Among many potential problems to solve for the reduced deflect density in III-nitride thin film growth substrate surface structures and morphologies in atomistic scale are essentially important topics. We especially noticed SiC surfaces, which normally show rather rough morphology at the as-received condition. We initially found that such surface features on just 6H-SiC(0001) were improved by high temperature (〜1400℃) hydrogen gas (with 〜14% HCl) etching, resulting in atomically smooth surfaces. Indeed, this process affects the introduction of structural deflects in AIN and GaN hetero-thin films. Vicinal substrates, 4-degree-off 6H-SiC(0001) and 8-degree-off 4H-SiC(0001), were also etched to see if similar smoothening effects were observed. Both vicinal SiC surfaces indicated regularly spaced step/terrace structures in nanometer scale. The origins of such ordering structures were investigated and found that the surfaces consist of nanofacets; (0001) and (11-2n), due to surface phase separation in minimizing surface free energies. The ordering of such nanofacet pairs is considered with quantum step bunching and facet-facet interactions. Importantly the former is greatly attributed to superior periodicity compared to conventional cubic semiconductors (Si and GaAs), owing to polytymorpholic nature of SiC. We investigated GaN nucleation and growth on vicinal SiC surfaces with periodic nanofacets and showed anisotropic structural characteristics and thus implication of reduction of the defect density.
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