The role of the low temperature buffer layer and layer thickness in the optimization of OMVPE growth of GaN on sapphire |
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Authors: | S D Hersee J Ramer K Zheng C Kranenberg K Malloy M Banas M Goorsky |
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Affiliation: | (1) Center for High Technology Materials, University of New Mexico, 87131 Albuquerque, NM;(2) Department of Materials Science and Engineering, University of California, 90095-1595 Los Angeles, CA |
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Abstract: | In agreement with previous work,12 a thin, low temperature GaN buffer layer, that is used to initiate OMVPE growth of GaN growth on sapphire, is shown to play
a critical role in determining the surface morphology of the main GaN epilayer. X-ray analysis shows that the mosaicity of
the main GaN epilayer continues to improve even after several μm of epitaxy. This continuing improvement in crystal perfection
correlates with an improvement in Hall mobility for thicker samples. So far, we have obtained a maximum mobility of 600 cm2/V-s in a 6 μm GaN epilayer. Atomic force microscopy (AFM) analysis of the buffer layer and x-ray analysis of the main epilayer
lead us to conclude that the both of these effects reflect the degree of coherence in the main GaN epitaxial layer. These
results are consistent with the growth model presented by Hiramatsu et al., however, our AFM data indicates that for GaN buffer
layers partial coherence can be achieved during the low temperature growth stage. |
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Keywords: | GaN metalorganic chemical vapor deposition (MOCVD) mobility |
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