Temperature dependence of the interband critical points of bulk Ge and strained Ge on Si
| Autor: | Cayla M. Nelson, Nalin Fernando, Jose Menendez, Amber A. Medina, Chi Xu, Stefan Zollner, John Kouvetakis, Jacqueline A. Cooke, Ayana Ghosh, T. Nathan Nunley |
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| Rok vydání: | 2017 |
| Předmět: |
010302 applied physics
Diffraction Materials science Condensed matter physics General Physics and Astronomy chemistry.chemical_element Biaxial tensile test Germanium 02 engineering and technology Surfaces and Interfaces General Chemistry 021001 nanoscience & nanotechnology Condensed Matter Physics Epitaxy 01 natural sciences Thermal expansion Critical point (mathematics) Surfaces Coatings and Films Condensed Matter::Materials Science Reciprocal lattice chemistry 0103 physical sciences 0210 nano-technology Electronic band structure |
| Zdroj: | Applied Surface Science. 421:905-912 |
| ISSN: | 0169-4332 |
| Popis: | Epitaxial Ge layers on a Si substrate experience a tensile biaxial stress due to the difference between the thermal expansion coefficients of the Ge epilayer and the Si substrate, which can be measured using asymmetric X-ray diffraction reciprocal space maps. This stress depends on temperature and affects the band structure, interband critical points, and optical spectra. This manuscripts reports careful measurements of the temperature dependence of the dielectric function and the interband critical point parameters of bulk Ge and Ge epilayers on Si using spectroscopic ellipsometry from 80 to 780 K and from 0.8 to 6.5 eV. The authors find a temperature-dependent redshift of the E1 and E1 + Δ1 critical points in Ge on Si (relative to bulk Ge). This redshift can be described well with a model based on thermal expansion coefficients, continuum elasticity theory, and the deformation potential theory for interband transitions. The interband transitions leading to E 0 ′ and E2 critical points have lower symmetry and therefore are not affected by the stress. |
| Databáze: | OpenAIRE |
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