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Forbidden energy gap between valence band and conduction band is least in the case of _____.
- a)Mica
- b)Pure silicon
- c)Pure germanium
- d)Impure silicon
Correct answer is option 'D'. Can you explain this answer?
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Forbidden energy gap between valence band and conduction band is least...
Forbidden energy gap between valence band and conduction band is least in the case of impure silicon.
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Forbidden energy gap between valence band and conduction band is least...
Forbidden energy gap between valence band and conduction band is least in the case of impure silicon. This is due to the following reasons:
1. Impurities introduce energy levels: When impurities are added to silicon, they introduce new energy levels within the forbidden energy gap. These energy levels are known as dopant levels. The impurities can be either donors (such as phosphorus) or acceptors (such as boron). Donors introduce energy levels closer to the conduction band, while acceptors introduce energy levels closer to the valence band.
2. Bandgap narrowing: The presence of dopant levels causes the bandgap to narrow. This is because the dopant levels can overlap with the valence or conduction band, reducing the energy required for an electron to jump from the valence band to the conduction band. As a result, the forbidden energy gap between the valence band and conduction band is reduced.
3. Increased carrier concentration: Impurities also increase the carrier concentration in the material. Donors introduce free electrons, while acceptors create holes (or vacancies in the valence band). The increased carrier concentration enhances the conductivity of the material.
Overall, impurities in silicon reduce the forbidden energy gap between the valence and conduction bands, making it easier for electrons to move from the valence band to the conduction band. This is why the forbidden energy gap is least in impure silicon.
1. Impurities introduce energy levels: When impurities are added to silicon, they introduce new energy levels within the forbidden energy gap. These energy levels are known as dopant levels. The impurities can be either donors (such as phosphorus) or acceptors (such as boron). Donors introduce energy levels closer to the conduction band, while acceptors introduce energy levels closer to the valence band.
2. Bandgap narrowing: The presence of dopant levels causes the bandgap to narrow. This is because the dopant levels can overlap with the valence or conduction band, reducing the energy required for an electron to jump from the valence band to the conduction band. As a result, the forbidden energy gap between the valence band and conduction band is reduced.
3. Increased carrier concentration: Impurities also increase the carrier concentration in the material. Donors introduce free electrons, while acceptors create holes (or vacancies in the valence band). The increased carrier concentration enhances the conductivity of the material.
Overall, impurities in silicon reduce the forbidden energy gap between the valence and conduction bands, making it easier for electrons to move from the valence band to the conduction band. This is why the forbidden energy gap is least in impure silicon.
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Forbidden energy gap between valence band and conduction band is least in the case of _____.a)Micab)Pure siliconc)Pure germaniumd)Impure siliconCorrect answer is option 'D'. Can you explain this answer?
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