(a)
Interpretation:
The valence band, conduction band, and band gap in the given figure has to be identified.
Concept introduction:
Valence band:
Valence band is defined as valence electron orbital of an element. It is a bunch of orbitals from which electrons shift to conduction band when excitation occurs. Conduction band and valence band are combined together in conductors. In semiconductors, there is a small band gap which separates conduction band and valence band.
Conduction band:
It is a bunch of orbitals into which electrons shift from valence band when excitation occurs. Electrons present in conduction band are free to move which creates
Band gap:
Band gap is the difference in energy between conduction band and valence band. In semiconductors, there is a small band gap which separates conduction band and valence band.
(b)
Interpretation:
The change in electron population when silicon dopes with gallium has to be drawn.
Concept introduction:
Valence band:
Valence band is defined as valence electron orbital of an element. It is a bunch of orbitals from which electrons shift to conduction band when excitation occurs. Conduction band and valence band are combined together in conductors. In semiconductors, there is a small band gap which separates conduction band and valence band.
Conduction band:
It is a bunch of orbitals into which electrons shift from valence band when excitation occurs. Electrons present in conduction band are free to move which creates electric current.
Band gap:
Band gap is the difference in energy between conduction band and valence band. In semiconductors, there is a small band gap which separates conduction band and valence band
(c)
Interpretation:
The change in electron population when silicon dopes with arsenic has to be drawn.
Concept introduction:
Valence band:
Valence band is defined as valence electron orbital of an element. It is a bunch of orbitals from which electrons shift to conduction band when excitation occurs. Conduction band and valence band are combined together in conductors. In semiconductors, there is a small band gap which separates conduction band and valence band.
Conduction band:
It is a bunch of orbitals into which electrons shift from valence band when excitation occurs. Electrons present in conduction band are free to move which creates electric current.
Band gap:
Band gap is the difference in energy between conduction band and valence band. In semiconductors, there is a small band gap which separates conduction band and valence band
(d)
Interpretation:
The electrical conductivity of doped silicon and pure silicon has to be compared. Also the differences has to be explained.
Concept introduction:
Valence band:
Valence band is defined as valence electron orbital of an element. It is a bunch of orbitals from which electrons shift to conduction band when excitation occurs. Conduction band and valence band are combined together in conductors. In semiconductors, there is a small band gap which separates conduction band and valence band.
Conduction band:
It is a bunch of orbitals into which electrons shift from valence band when excitation occurs. Electrons present in conduction band are free to move which creates electric current.
Band gap:
Band gap is the difference in energy between conduction band and valence band. In semiconductors, there is a small band gap which separates conduction band and valence band.
Effect of change in temperature:
Increase in temperature increases electrical conductivity of semiconductors because when temperature raises, there will be more electrons in conduction band and hole in valance band. On the other hand, electrical conductivity decreases when temperature increases due to increased vibrational motion of metal cation around lattice leads to disruption of flow of electrons in crystal.
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