18 August 2009 Nanoscale InGaN/GaN on ZnO substrate for LED applications
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The challenge of growing GaN and its alloys, In1-xGaxN and Al1-xGaxN, is still formidable because of the lack of close lattice match, stacking order match, and similar thermal expansion coefficient substrates, the same as GaN-based optoelectronic materials. ZnO is the most promising optoelectronic materials in the next generation, with wide band gap of 3.3eV and exciton binding energy of 60meV. In addition, ZnO also has been considered as a substrate for epitaxial growth of III-Nitrides due to its close lattice and stacking order match. Our works cover the growth of n-type InGaN and GaN epitaxial layers on lattice-matched ZnO substrates by metal-organic chemical vapor deposition (MOCVD). Since MOCVD is the dominant growth technology for GaN-based materials and devices, there is a need to more fully explore this technique for ZnO substrates. However, the thermal stability of the ZnO substrate, out-diffusion of Zn from the ZnO into the GaN, and H2 back etching into the substrate can cause growth of poor quality GaN. We use a GaN buffer layer of about 40nm to avoid Zn/O diffusion. We can investigate the Zn/O diffusion in the InGaN epilayers by means of second ion mass spectroscopy (SIMS) depth profiles, and analyze the surface bonding of different elements by x-ray photoelectron spectroscopy (XPS), and investigate optical and structural characterization of InGaN epilayers on ZnO substrates by various angles spectroscopic ellipsometry (VASE). Finally, from the Raman scattering, Photoluminescence (PL) and Photoluminescence excitation (PLE) spectra, we can determine the qualities easily and prove that we have grown the InGaN on ZnO with a GaN buffer layer successfully.
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I-Hsiang Hung, I-Hsiang Hung, You-Ren Lan, You-Ren Lan, Tsung Han Wu, Tsung Han Wu, Zhe Chuan Feng, Zhe Chuan Feng, Nola Li, Nola Li, Hongbo Yu, Hongbo Yu, Ian T. Ferguson, Ian T. Ferguson, Weijie Lu, Weijie Lu, } "Nanoscale InGaN/GaN on ZnO substrate for LED applications", Proc. SPIE 7422, Ninth International Conference on Solid State Lighting, 74220K (18 August 2009); doi: 10.1117/12.825851; https://doi.org/10.1117/12.825851

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