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I'm a high school student, and I was researching about oxide semiconductors and thin-film transistors when I found something confusing. Here's what I know: Normally, doping semiconductors causes the conductivity of the material. However, a large band gap requires more energy for an electron to move to the conduction band, resulting in less current, and making it harder for electrons to flow.

In oxide semiconductors, oxide materials are doped, but they have a large band gap of more than $3 \ \text{eV}$, and yet they have high conductivity. Something seems to be missing, and I'll be happy for any advice or points at misconceptions. Thank you!

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The dopants create energy levels inside the band gap. This makes it much easier to promote electrons to the conduction band (or holes to the valance band). Search "dopant level" on this site for similar questions, some with diagrams.

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  • $\begingroup$ I think I understand what you mean, but I have another question : why is having a wide band gap an appealing factor for a semiconductor? Is it because the oxide semiconductor can be transparent and also have high conductivity(due to dopant level)? Thanks in advance! $\endgroup$
    – 0LStack
    Commented Dec 25, 2021 at 7:00
  • $\begingroup$ @0LStack There are entire courses (and books) that deal with applications of this stuff. But for instance, a band gap is crucial for making digital logic work with the p-n junction. By doping differently, you can make a connection that only lets current flow one way $\endgroup$
    – HiddenBabel
    Commented Dec 26, 2021 at 2:28

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