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(a) Scanning electron microscope image of the tensile-strained germanium waveguide. (b) Two-dimensional profile of the hydrostatic strain component in the germanium film. The width of the waveguide is 4 μm. The hydrostatic stress in the nitride film is 4.5 GPa. The right scale corresponds to the amplitude of the hydrostatic strain component.
(a) left: Room temperature photoluminescence spectra for variable waveguide widths. The smooth lines correspond to the modeling. The initial hydrostatic stress in the nitride film is 3 GPa. (b) Same as in (a), but for the 4.5 GPa nitride stressor. The curves have been offset for clarity. The difference in the thickness of the nitride layer contributes to the difference in amplitude. The indirect band gap recombination at low energy is not taken into account in the modeling.
Room temperature photoluminescence spectra for samples with variable widths and distinct orientations. The thick lines correspond to the 〈100〉 ridge direction. The dashed lines correspond to the 〈110〉 direction. The curves have been offset for clarity. The inset shows schematically the effect of the orientation on the energy splitting.
Calculated room temperature ratio between the electron concentration in the Γ valley and the total electron concentration as a function of the uniaxial strain. The calculation is performed for two distinct orientations of the ridge. The inset shows the comparison between the predicted photoluminescence amplitude ratio between 〈100〉 and 〈110〉 orientations (full line) and the experimental data (squares).
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