I need the answer only for last two parts (c and d), thanks! Silicon has a band-

Question

I need the answer only for last two parts (c and d), thanks!

Silicon has a band-gap of 1.1 eV. This means that a photon with AT LEAST 1.1 eV is needed to excite an electron from the valence band (fully occupied band) to the conduction band (unoccupied).

a) If a photon has an energy of 1.1 eV, what is it wavelength in nanometers?

b) Where is the photon relative to visible spectrum?

c) If many 0.55 eV photons (say 1.0 million) strike the silicon, how many electrons will be excited into the conduction band?

d) If a photon with an energy of 1.5 eV strikes the silicon, what happens to the extra 0.4 eV (1.5 – 1.1 eV)?

Explanation / Answer

(A) E = h c / lambda

1.1 x 1.6 x 10^-19 = (6.626 x 10^-34)(3 x 10^8) / lambda

lambda = 1129.4 x 10^-9 m or 1129.4 nm

(B) It is in infrared region.

(C) 0.55 eV is less than minimum energy needed for excitation.

hence no electron will get excited.

(d) that 0.4 eV energy will go into the kinetic energy of ejected electron.

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