Comparison between the values of the E1 and E1 + Δ1 critical point energies for Si1−xGex alloys for unstrained alloys and those calculated using the elastic theory described in Sec. II for pseudomorphic, bi-axially strained Si1−xGex alloys on Si(001). The experimental values were taken from Ref.10.
Symmetric 004, ω-2θ rocking curves of Si1−xGex alloy films for selected Ge concentrations from x = 0.05 to x = 0.75.
004 and 224 reciprocal space maps were plotted in hkl crystallographic dimensions showing the pseudomorphic nature of Si1−xGex (x = 0.3 and x = 0.7) alloys on Si (001). The 004 RSMs characterize the Si1−xGex 004 lattice planes that are parallel to the Si 004 lattice planes while the 224RSM characterizes lattice both parallel and perpendicular to surface normal.
The complex refractive index of Si1−xGex alloys for selected concentrations of germanium.
The complex dielectric function of Si1−xGex alloys for selected concentrations of germanium.
Comparison of the dielectric function of pseudomorphic Si1−xGex alloys films with strain free Si1−xGex alloys. The effect of strain on the line shape of the E1 critical point is evident as the concentration of Ge increases. “Hum” refers to Humlíček's data for un-strained Si1−xGex alloy layer.10
Comparison between the experimental values of the E1 and E1 + Δ1 critical point energies for pseudomorphic, bi-axially strained Si1−xGex alloys grown on Si(001)Si1−xGex and the elastic theory described in Sec. II. The elastic theory results were calculated using the exact k*p expression for the energy shifts.
Elastic constants, phonon deformation potentials, and lattice constant values for silicon and germanium at room temperature. Values are taken from Refs. 1 and 19.
Measured and calculated values of the energies of the E1 and E1 + Δ1 critical points for pseudomorphic Si1−xGex on Si(001). The k*p theory results are listed along with the values obtained using the small and high shear approximations. The germanium concentration and thickness for the Si1−xGex films measured in this study are listed. The concentration and thickness data have a relative total error of 0.5 atomic % or better. Thus, for x = 0.10, the Ge percentage is 10 ± 0.5% and for x = 0.7 the Ge percentage is 70 ± 3.5%.
Comparison of experimental E1 and E1 + Δ1 critical point energies with literature values. Comparison data have been shown only for the samples that exactly match the Ge concentrations published in the above mentioned references. The samples characterized in Ref. 1 were capped with an epitaxial silicon layer making determination of E1 and E1 + Δ1 difficult due to the overlap with E0′. In addition, the silicon capping layer may affect the stress experienced by the Si1−xGex alloys making comparison difficult.
Comparison of critical point values extracted using second and third derivative analysis techniques.
The real ε1 and imaginary ε2 parts of the dielectric function for pseudomorphic Si1−xGex alloys.
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