Condensed matter physics Thin films micro-Raman spectroscopy x-ray diffraction
T.S. Perova, J. Wasyluk, K. Lyutovich, E. Kasper, M. Oehme, K. Rode and A. Waldron, Composition and strain in thin Si1-xGex virtual substrates measured by micro-Raman spectroscopy and X-ray diffraction, Journal of Applied Physics, 109, 2011, 033502/1-11
Journal of Applied Physics 109
Micro-Raman spectroscopy was employed for the determination of the germanium content, x and
strain, , in ultrathin SiGe virtual substrates grown directly on Si by molecular beam epitaxy. The
growth of highly relaxed SiGe layers was achieved by the introduction of point defects at a very low
temperature during the initial stage of growth. SiGe virtual substrates with thicknesses in the range
40–200 nm with a high Ge content up to 50% and degree of relaxation, r, in the range 20%–100%
were investigated using micro-Raman spectroscopy and x-ray diffraction XRD techniques. The Ge
content, x, and strain, , were estimated from equations describing Si–Si, Si–Ge, and Ge–Ge Raman
vibrational modes, modified in this study for application to thin SiGe layers. The alteration of the
experimentally derived equations from previous studies was performed using independent data for
x and r obtained from XRD reciprocal space maps. A number of samples consisting of a
strained-silicon s-Si layer deposited on a SiGe virtual substrate were also analyzed. The stress
value for the s-Si varied from 0.54 to 2.75 GPa, depending on the Ge-content in the virtual
substrates. These results are in good agreement with theoretically predicted values.
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