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Effects of stress on the dielectric function of strained pseudomorphic Si1−xGex alloys from 0 to 75% Ge grown on Si (001)
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10.1063/1.4751275
/content/aip/journal/jap/112/5/10.1063/1.4751275
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/5/10.1063/1.4751275

Figures

Image of FIG. 1.
FIG. 1.

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.

Image of FIG. 2.
FIG. 2.

Symmetric 004, ω-2θ rocking curves of Si1−xGex alloy films for selected Ge concentrations from x = 0.05 to x = 0.75.

Image of FIG. 3.
FIG. 3.

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.

Image of FIG. 4.
FIG. 4.

The complex refractive index of Si1−xGex alloys for selected concentrations of germanium.

Image of FIG. 5.
FIG. 5.

The complex dielectric function of Si1−xGex alloys for selected concentrations of germanium.

Image of FIG. 6.
FIG. 6.

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

Image of FIG. 7.
FIG. 7.

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.

Tables

Generic image for table
Table I.

Elastic constants, phonon deformation potentials, and lattice constant values for silicon and germanium at room temperature. Values are taken from Refs. 1 and 19.

Generic image for table
Table II.

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%.

Generic image for table
Table III.

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.

Generic image for table
Table IV.

Comparison of critical point values extracted using second and third derivative analysis techniques.

Generic image for table
Table V.

The real ε1 and imaginary ε2 parts of the dielectric function for pseudomorphic Si1−xGex alloys.

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/content/aip/journal/jap/112/5/10.1063/1.4751275
2012-09-11
2014-04-20
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Effects of stress on the dielectric function of strained pseudomorphic Si1−xGex alloys from 0 to 75% Ge grown on Si (001)
http://aip.metastore.ingenta.com/content/aip/journal/jap/112/5/10.1063/1.4751275
10.1063/1.4751275
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