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Some sites claim that crystalline silicon has a band gap of approximately $1$ to $1.2$ or so electron volts, and others say it is about $3$ to $3.4$ eV....

Amorphous silicon is usually described as having a gap of about $1.75$ eV, although I am not sure if this is for hydrogenated Si or not....

Is the lower figure for direct band gap crystalline silicon, and the higher for indirect?

Does the doping of crystalline silicon make it a direct band gap semiconductor?

I am confused.....

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    $\begingroup$ I wouldn't trust a random online site for material properties; look to peer-reviewed resources such as textbooks. Do you find a discrepancy there? If so, please give the citation information. Also, please ask one question at a time. $\endgroup$
    – Chemomechanics
    Commented Nov 27, 2021 at 17:33
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    $\begingroup$ Find a picture of a silicon wafer. An examination of the photo should answer the question. $\endgroup$
    – garyp
    Commented Nov 28, 2021 at 14:34

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The band gap of crystalline Si at 300 K is 1.12 eV. Here is an authoritative source for band structure information. Crystalline silicon is an indirect band gap semiconductor. Doping does not change that.

If I had to guess the source of the confusion, it's direct vs indirect bandgap. If you look at the spacing between the bands at $\vec{k}=0$, it's about 3.4 eV (called $E_{\Gamma 1}$ here). That's kind of what the bandgap would be if Si were a direct bandgap material (and the gap at $\vec{k}=0$ is important for some purposes).

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