Investigation of Composition-dependent Optical Phonon Modes in AlxGa1-xN Epitaxial Layers Grown on Sapphire Substrates

Abstract

We reported the systematical study of optical properties of hexagonal AlxGa1−xN epitaxial films grown on c-sapphire substrate using metal-organic chemical vapor deposition. By performing Fourier transform infrared spectroscopy measurements, the high-frequency dielectric constants and phonon frequencies can be obtained by theoretically fitting the experimental infrared reflectance spectra using a four-phase layered model. The high-frequency dielectric constant of AlxGa1−xN varies between 4.98 and 4.52 for ε ∞,⊥ (polarization perpendicular to the optical axis) and between 4.95 and 4.50 for ε ∞,// (polarization parallel to the optical axis) respectively when the aluminum composition changes from 0.15 to 0.24. Furthermore, from experimental infrared reflectance spectra of AlxGa1−xN films, a specific absorption dip at 785 cm−1 was observed when the aluminum composition is larger than 0.24. The dip intensity increases and the dip frequency shifts from 785 to 812 cm−1 as aluminum composition increases from 0.24 to 0.58. According to the reciprocal space map of x-ray diffraction measurements, the emergence of this dip could be resulted from the effects of strain relaxation in AlGaN epitaxial layers due to the large lattice mismatch between GaN and AlGaN epitaxial film.

This is a preview of subscription content, access via your institution.

References

  1. 1

    G. Sun, R. A. Soref, and J. B. Khurgin, Superlattice. Microstruct. 37, 107 (2005).

    CAS  Article  Google Scholar 

  2. 2

    G. Yu, H. Ishikawa, M. Umeno, T. Egawa, J. Watanabe, T. Soga, and T. Jimbo, Appl. Phys. Lett. 73, 1472 (1998).

    CAS  Article  Google Scholar 

  3. 3

    M. Holtz, T. Prokofyeva, M. Seon, K. Copeland, J. Vanbuskirk, S. Williams, S. A. Nikishin, V. Tretyakov, and H. Temkin, J. Appl. Phys. 89, 7977 (2001).

    CAS  Article  Google Scholar 

  4. 4

    Z. G. Hu, M. Strassburg, N. Dietz, A. G. U. Perera, A. Asghar and I. T. Ferguson, Phys. Rev. B 72, 245326 (2005).

    Article  Google Scholar 

  5. 5

    G. S. Huang, H. H. Yao, T. C. Lu, H. C. Kuo, and S. C. Wang, J. Appl. Phys. 99, 104901 (2006).

    Article  Google Scholar 

  6. 6

    M. Schubert, Phys. Rev. B 53, 4265 (1996).

    Article  Google Scholar 

  7. 7

    Z. G. Hu, M. Strassburg, A. Weerasekara, N. Dietz, A. G. U. Perera, M. H. Kane, A. Asghar, and I. T. Ferguson, Appl. Phys. Lett. 88, 061914 (2006).

    Article  Google Scholar 

  8. 8

    D. W. Berreman and F. C. Unterwald, Phys. Rev. 174, 791 (1968).

    CAS  Article  Google Scholar 

  9. 9

    A. Kasic, M. Schubert, S. Einfeldt, D. Hommel, and T. E. Tiwald, Phys. Rev. B 62, 7365 (2000).

    Article  Google Scholar 

  10. 10

    M. Schubert, T. E. Tiwald, and C. M. Herzinger, Phys. Rev. B 61, 8187 (2000).

    Article  Google Scholar 

  11. 11

    W. H. Press, S. A. Teukolsky, W. T. Vetterling, and B. P. Flannery, Numerical Recipes in C: The Art of Scientific Computing, Cambridge, Cambridge University Press, MA, 1992.

    Google Scholar 

Download references

Author information

Affiliations

Authors

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Chen, JR., Lu, TC., Kuo, HC. et al. Investigation of Composition-dependent Optical Phonon Modes in AlxGa1-xN Epitaxial Layers Grown on Sapphire Substrates. MRS Online Proceedings Library 1167, 705 (2009). https://doi.org/10.1557/PROC-1167-O07-05

Download citation