| Project/Area Number |
17560024
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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 |
Thin film/Surface and interfacial physical properties
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| Research Institution | Kumamoto University |
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Principal Investigator |
KURODA Noritaka Kumamoto University, Graduate School of Science and Technology, Professor, 自然科学研究科, 教授 (40005963)
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| Co-Investigator(Kenkyū-buntansha) |
HIROYUKI Yokoi Kumamoto University, Graduate School of Science and Technology, Associate Professor, 自然科学研究科, 助教授 (50358305)
WATANABE Junji Kumamoto University, Graduate School of Science and Technology, Professor, 自然科学研究科, 教授 (40281076)
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| Project Period (FY) |
2005 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 2006: ¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 2005: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Keywords | GaN / ZnO / Zn_<1-x>Mg_xO / hetero-reststrahlen band / surface polariton / oblique-incidence infrared reflection / attenua ted total reflection / light emitting diodes / ZnMgO / 薄膜 / 結晶品位 / シート電子密度 / Gan / サファイア基板 / 光学フォノン |
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| Research Abstract |
Quality of crystal lattices of GaN/sapphire, ZnO/sapphire and ZnMgO/ZnO/sapphire has been examined by infrared spectroscopy. The GaN films of GaN/sapphire have been grown by MOCVD to a thickness of 2.0-2.4 μm. It emerges from the oblique-incidence, heterogeneous reststrahlen spectrum that the d imping energies of polar optical phonons are markedly graded along the growth direction of the film, showing that the GaN film has a very high quality in the surface region of the thickness of about 1 μm, while the lattices beneath the surface region down to the buffer layer remain significantly strained because of the lattice mismatch against the sapphire substrate. These implications are confirmed from properties of the surface polaritons, which are observed by the attenuated total reflection spectroscopy, on the interface between GaN and sapphire substrate.
Similar expe-iments have been carried out for MBE grown ZnO/sapphire and ZnMgO/ZnO/sapphire: The thickness of ZnMgO is 100 to 200 nm, whil
… More
e the thickness of ZnO film is in a range of 500 to 1000 nm in both substances. Despite of the small thickness of the films, in the p-polarization the uらper branch of the A_1(L0)-plasmon coupled mode is observed as a prominent dip in the oblique-incidence reststrahlen spectrum in any samples. It appears from comparison of the energy shift of this mode with the values of the Hall concentration that electrons are rather confined in narrow interface zones of ZnO/sapphire and ZnMgO/ZnO. It also appears from the oblique-incidence reflection spectrum that there exists a good correlation of the damping energy of the E_1(LO) mode with the
In addition, ZnO crystals grown on a silica substrate by a chemical vapor transport have also been examined. The crystals are grown with a diameter of 60 to 80 μm into a height of 5 to 15 μm. Our microscopic FTIR spectrometer successfully yields the hetero-reststrahlen spectrum of these mesoscopic crystals. It is found that the infrared dielectric constant, ε_<001>, varies significantly from sample to sample around the value, 3.7, of a good bulk crystal, thoughthe crystals are all grown with the c-axis of wurtzite structure normal to the silica substrate. The reason of this finding is to be studied further. Less
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