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Nanomaterials 2018, 8(9), 704; https://doi.org/10.3390/nano8090704

Structural and Stress Properties of AlGaN Epilayers Grown on AlN-Nanopatterned Sapphire Templates by Hydride Vapor Phase Epitaxy

1
Department of Materials Science and Engineering, National Chung Hsing University, Taichung 40227, Taiwan
2
Department of Materials Science and Engineering, Da-Yeh University, Changhua 51591, Taiwan
3
Department of Industrial Engineering and Management, Da-Yeh University, Changhua 51591, Taiwan
4
Department of Electronics Engineering, National Chiao Tung University, Hsinchu 300, Taiwan
5
Research Center for Sustainable Energy and Nanotechnology, National Chung Hsing University, Taichung 40227, Taiwan
6
Innovation and Development Center of Sustainable Agriculture, National Chung Hsing University, Taichung 40227, Taiwan
*
Author to whom correspondence should be addressed.
Received: 22 July 2018 / Revised: 29 August 2018 / Accepted: 8 September 2018 / Published: 10 September 2018
(This article belongs to the Special Issue Synthesis and Modification of Nanostructured Thin Films)
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Abstract

In this paper, we report the epitaxial growth and material characteristics of AlGaN (Al mole fraction of 10%) on an AlN/nanopatterned sapphire substrate (NPSS) template by hydride vapor phase epitaxy (HVPE). The crystalline quality, surface morphology, microstructure, and stress state of the AlGaN/AlN/NPSS epilayers were investigated using X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The results indicate that the crystal quality of the AlGaN film could be improved when grown on the AlN/NPSS template. The screw threading dislocation (TD) density was reduced to 1.4 × 109 cm−2 for the AlGaN epilayer grown on the AlN/NPSS template, which was lower than that of the sample grown on a flat c-plane sapphire substrate (6.3 × 109 cm−2). As examined by XRD measurements, the biaxial tensile stress of the AlGaN film was significantly reduced from 1,187 MPa (on AlN/NPSS) to 38.41 MPa (on flat c-plane sapphire). In particular, an increase of the Al content in the overgrown AlGaN layer was confirmed by the TEM observation. This could be due to the relaxation of the in-plane stress through the AlGaN and AlN/NPSS template interface. View Full-Text
Keywords: AlGaN; nanopatterned sapphire substrate; hydride vapor phase epitaxy; stress; transmission electron microscopy AlGaN; nanopatterned sapphire substrate; hydride vapor phase epitaxy; stress; transmission electron microscopy
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Tasi, C.-T.; Wang, W.-K.; Ou, S.-L.; Huang, S.-Y.; Horng, R.-H.; Wuu, D.-S. Structural and Stress Properties of AlGaN Epilayers Grown on AlN-Nanopatterned Sapphire Templates by Hydride Vapor Phase Epitaxy. Nanomaterials 2018, 8, 704.

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