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Valance Bands & Energy to Produce and Electron Hole Pair

3. A material has an effectively full valence band and an empty conduction band. Explain why that if these two bands overlap the material behaves as a metal and if they are separated by a few electron volts in energy the material is an insulator.

4. Calculate the minimum energy a photon must have to produce an electron hole pair in an extrinsic semiconductor of band gap 1.0 electron volts.

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Please see the attached file.

3. A material has an effectively full valence band and an empty conduction band. Explain why that if these two bands overlap the material behaves as a metal and if they are separated by a few electron volts in energy the material is an insulator.
Answer:

Explanation for why if these two bands overlap the material behaves as a metal:

When electron is in valence band, it can not contribute to the conduction process. But when it gets excited to conduction band, it contributes in the conduction process.

Consider the situation when completely filled valence band and an empty conduction band overlap. If there are N number of atoms in the metal, then there are N energy levels in a valence band and N energy states in empty conduction band. The ...

Solution Summary

Word file explains the effects of overlapping valence and conduction bands and calculates the minimum energy a photon must have for an electron hole pair in a semiconductor.

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