What do the peaks in the reflectance spectrum of silicon samples represent?

[hjelmgart]

Hello,

I am currently analysing some relfectance data I obtained from measurements on several silicon samples. During the process I used the standard fresnel coefficients, and suddenly I began to wonder, what the peaks describe? The last graph at this link shows it for normal incident light, I think.

My typical approach is to relate peaks to the band gap, but then I remembered silicon has a band gap of 1,1 eV.

So what explains the peaks? I am still thinking, that it is related to the band gap. But the band gap isn't constant either? The 1,1 eV is just the lowest gap, right?

So do the peaks represent different band gaps with respect to the brillouin zone, or how is it?

Any suggestions or explanations appreciated! Or possibly a source, that explains it, as I so far had no luck at finding such.

 

[Claude Bile]

One reflectivity peak is due to a peak in the real refractive index, the other is due to a peak in the imaginary refractive index: and that the formula for calculating reflectivity applies for real- and complex-valued refractive indices.

Note too, that the real and imaginary refractive index components are linked via the Kramers-Kronig relations.

Claude.