Question

The energy gap for silicon at 300 k is 1.14 ev. (a) find the lowest frequency photon that will promote an electron in silicon from the valence band to the conduction band.

Answer 1

Answer:

$2.74\cdot 10^{14} Hz$

Explanation:

First of all, let's convert the energy gap from eV to Joules:

$E=1.14 eV \cdot (1.6\cdot 10^{-19}J/eV)=1.82\cdot 10^{-19}J$

In order to promote the electron to the conduction band, the electron must absorb a photon with an energy at least equal to the energy gap, so:

$E=hf=1.82\cdot 10^{-19}J$

where

h is the Planck constant

f is the frequency of the photon

Solving for f, we find the lowest frequency needed:

$f=\frac{E}{h}=\frac{1.82\cdot 10^{-19} J}{6.63\cdot 10^{-34}Js}=2.74\cdot 10^{14} Hz$