Question

If photons with energy of 0.7 eV was applied to A Si Wafer is at 0k (E_gfor Si =1.12eV), the valence and conduction band are

please explain your answers

(I)

Both are completely empty

Both are completely filled.

Both are partially empty.

Both are partially filled.

None of the above

All of the above 1-4.

(II)

CB band is completely empty and VB is completely filled.

VB band is completely empty and CB is completely filled.

CB band is partially empty and VB is completely filled.

VB band is partially empty and CB is completely filled.

None of the above

All of the above (1-4)

(III)

CB band is partially filled and VB is completely filled.

VB band is partially filled and CB is completely filled.

CB band is partially empty and VB is partially filled.

VB band is partially empty and CB is partially filled.

None of the above

All of the above (1-4)

Answer 1

As Eg for silicon is 1.12eV and we are applying a photon whose energy is only 0.7 eV it means these phots will not be able to give enough energy to take out the electrons from valence band so that they can go into the conduction band.

i) Answer will be none of the above

2)Conduction band is empty completely and valence band is completely filled because all electrons are in thier ground state and not in the excited state because photons do not have the sufficient energy to energize the electrons.

iii) VB band is partially empty and CB band is partially filled this situation will only happen when some of the electrons in valence band will get sufficient energy and jump from Valence band to conduction band.