Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy
Abstract
Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.
- Authors:
-
- Department of Physics, Microelectronics Research Group, University of Crete, P.O. Box 2208, GR 71003, Greece and IESL, FORTH, P.O. Box 1385, GR71110 Heraklion (Greece)
- Physics Division, School of Technology, Aristotle University of Thessaloniki, GR54124 Thessaloniki (Greece)
- Publication Date:
- OSTI Identifier:
- 22304248
- Resource Type:
- Journal Article
- Journal Name:
- Journal of Applied Physics
- Additional Journal Information:
- Journal Volume: 115; Journal Issue: 21; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-8979
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ANISOTROPY; ASYMMETRY; ATOMIC FORCE MICROSCOPY; DIFFUSION; DISLOCATIONS; GALLIUM NITRIDES; MICROSTRUCTURE; MOLECULAR BEAM EPITAXY; RAMAN SPECTROSCOPY; RELAXATION; RESIDUAL STRESSES; RESOLUTION; SAPPHIRE; SPACE DEPENDENCE; SUBSTRATES; SURFACES; TRANSMISSION ELECTRON MICROSCOPY; X-RAY DIFFRACTION
Citation Formats
Lotsari, A., Kehagias, Th., Katsikini, M., Arvanitidis, J., Ves, S., Komninou, Ph., Dimitrakopulos, G. P., E-mail: gdim@auth.gr, Tsiakatouras, G., Tsagaraki, K., Georgakilas, A., and Christofilos, D. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy. United States: N. p., 2014.
Web. doi:10.1063/1.4880957.
Lotsari, A., Kehagias, Th., Katsikini, M., Arvanitidis, J., Ves, S., Komninou, Ph., Dimitrakopulos, G. P., E-mail: gdim@auth.gr, Tsiakatouras, G., Tsagaraki, K., Georgakilas, A., & Christofilos, D. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy. United States. https://doi.org/10.1063/1.4880957
Lotsari, A., Kehagias, Th., Katsikini, M., Arvanitidis, J., Ves, S., Komninou, Ph., Dimitrakopulos, G. P., E-mail: gdim@auth.gr, Tsiakatouras, G., Tsagaraki, K., Georgakilas, A., and Christofilos, D. 2014.
"Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy". United States. https://doi.org/10.1063/1.4880957.
@article{osti_22304248,
title = {Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy},
author = {Lotsari, A. and Kehagias, Th. and Katsikini, M. and Arvanitidis, J. and Ves, S. and Komninou, Ph. and Dimitrakopulos, G. P., E-mail: gdim@auth.gr and Tsiakatouras, G. and Tsagaraki, K. and Georgakilas, A. and Christofilos, D.},
abstractNote = {Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.},
doi = {10.1063/1.4880957},
url = {https://www.osti.gov/biblio/22304248},
journal = {Journal of Applied Physics},
issn = {0021-8979},
number = 21,
volume = 115,
place = {United States},
year = {Sat Jun 07 00:00:00 EDT 2014},
month = {Sat Jun 07 00:00:00 EDT 2014}
}