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Anisotropic Dielectric Properties of GaN Epilayers on Sapphire

Published online by Cambridge University Press:  01 February 2011

N. L. Rowell
Affiliation:
National Research Council, Ottawa, Ontario, Canada K1A 0R6
G. Yu
Affiliation:
National Research Council, Ottawa, Ontario, Canada K1A 0R6
D. J. Lockwood
Affiliation:
National Research Council, Ottawa, Ontario, Canada K1A 0R6
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Abstract

Polarized infrared reflectance from 300 to 1200 cm-1 at different incidence angles was measured at room temperature for sapphire and GaN/sapphire samples. A film of GaN was grown approximately 1.5 μm thick on c-plane sapphire by MOCVD with a thin GaN buffer layer. Because of the hexagonal structure of sapphire and GaN, their uniaxial optical properties are anisotropic. In the p-polarized reflective spectrum, we observed the mixed effect between the distinct infrared-active modes with dipole-moment oscillation perpendicular (E-mode) and parallel (A-mode) to the c axis. The contribution of the A-mode increased with increasing incidence angle. Therefore, we were able to obtain simultaneously the infrared dielectric functions parallel and perpendicular to the c axis, by fitting simultaneously three polarized reflectance spectra at three different incident angles with a suitable model. In the procedure, we adopted a new fitting technique, i.e., fitting the first numerical derivative of the polarized reflectance spectra to improve the accuracy of the phonon parameters and to overcome the inconsistency between the model and measurement in the whole frequency range. Excellent agreement has been obtained between the measured and fitted first derivative reflectance spectra for both the sapphire and GaN/sapphire samples. The dielectric information thus obtained for sapphire and GaN is of greater accuracy than those reported previously.

Type
Research Article
Copyright
Copyright © Materials Research Society 2004

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References

REFERENCES

1. Nakamura, S., Mukai, T., and Senoh, M., Appl. Phys. Lett, 174, 791 (1968).Google Scholar
2. Nakamura, S., Senoh, M., Nagahama, S. I., Iwasa, N., Yamada, T., Matsushita, T., Jiyoku, H., and Sugimoto, Y., Jpn. J. Appl. Phys., Part 2 35, L74 (1996).Google Scholar
3. Yu, G., Ishikawa, H., Egawa, T., Soga, T., Watanabe, J., Jimbo, T., and Umeno, M., Jpn. J. Appl. Phys. Part 2 36, L1029 (1997).Google Scholar
4. Kasic, A., Schubert, M., Einfeldt, S., and Hommel, D., Phys. Rev. B, 62, 7365 (2000).Google Scholar
5. Yu, G., Rowell, N. L., Lockwood, D. J. and Wasilewski, Z. R.; Appl. Phys. Lett. 83, 3683 (2003)Google Scholar
6. Yu, G., Rowell, N. L., Lockwood, D. J., and Poole, P. J., Appl. Phys. Lett., 81, 2175 (2002).Google Scholar
7. Schubert, M., Phys. Rev. B, 53, 4265 (1996).Google Scholar
8. Yu, G., Rowell, N. L., and Lockwood, D. J., J. Vacuum Sci. and Technol. A, submitted 2003.Google Scholar
9. Gervais, F., and Piriou, B., J. Phys. C 7, 2374 (1974).Google Scholar
10. Press, W. H., Flannery, B. P., Teukolsky, S. A. and Vetterling, W. T., Numerical Recipes: The Art of Scientific Computing (Cambridge University Press, Cambridge, England), 523ff.Google Scholar
11. Schubert, M., Tiwald, T. E., and Herzinger, C. M., Phys. Rev. B, 61, 8187 (2000).Google Scholar
12. Harima, H., J. Phys.: Condens. Matter 14, :R967 (2002).Google Scholar
13. Yu, G., Ishikawa, H., Umeno, M., Egawa, T., Watanabe, J., Soga, T., and Jimbo, T., Appl. Phys. Lett. 73, 1472 (1998).Google Scholar