Dixit, Ripudaman and Tyagi, Prashan and Kushvaha, Sunil Singh and Chockalingam, Sreekumar and Yadav, Brajesh Singh and Sharma, Nita Dilawar and Kumar, M. Senthil (2017) Influence of growth temperature on laser molecular beam epitaxy and properties of GaN layers grown on c-plane sapphire. Optical Materials, 66. pp. 142-148. ISSN 0925-3467

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We have investigated the influence of growth temperature on the in-plane strain, structural, optical and mechanical properties of heteroepitaxially grown GaN layers on sapphire (0001) substrate by laser molecular beam epitaxy (LMBE) technique in the temperature range 500-700 degrees C. The GaN epitaxial layers are found to have a large in-plane compressive stress of about 1 GPa for low growth temperatures but the strain drastically reduced in the layer grown at 700 degrees C. The nature of the in-plane strain has been analyzed using high resolution x-ray diffraction, atomic force microscopy (AFM), Raman spectroscopy and photoluminescence (PL) measurements. From AFM, a change in GaN growth mode from grain to island is observed at the high growth temperature above 600 degrees C. A blue shift of 20-30 meV in near band edge PL emission line has been noticed for the GaN layers containing the large in-plane strain. These observations indicate that the in-plane strain in the GaN layers is dominated by a biaxial strain. Using nanoindentation, it is found that the indentation hardness and Young's modulus of the GaN layers increases with increasing growth temperature. The results disclose the critical role of growth mode in determining the in-plane strain and mechanical properties of the GaN layers grown by LMBE technique.

Item Type: Article
Additional Information: Copyright for this article belongs to M/s Elsevier.
Subjects: Materials Science
Depositing User: Users 27 not found.
Date Deposited: 29 Oct 2018 11:05
Last Modified: 29 Oct 2018 11:05
URI: http://npl.csircentral.net/id/eprint/2746

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