A semiconductor has a band gap of 1.5 eV. What is the minimum wavelength in nm required to promote an electron from the valence to the conduction band?

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A semiconductor has a band gap of 1.5 eV. What is the minimum wavelength in nm required to promote an electron from the valence to the conduction band?

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Answer 1 · 2018-05-14T14:08:55

$λ = 827.5 n m$ $lambda = 827.5 nm$

Explanation:

To raise an electron from valence to conduction band , the energy required is

equal to the band gap in eV which has a value 1.5 eV as given

If a photon of energy E is absorbed by an electron then for the transfer

E = 1.5 eV = h. $ν$ $nu$ where h is plank's constant and

$ν$ $nu$ is the frequency.

as frequency $ν = \frac{c}{λ}$ $nu = c/ lambda$ ,therefore

$h . \frac{c}{λ}$ $h.c /lambda$ = 1.5 eV or

$λ = h . \frac{c}{1.5 e V}$ $lambda = h.c / (1.5 eV)$

substituting the values of h and c and eV in Joules we get

$λ$ $lambda$ = $\frac{(6.62 . 10^{- 34}) J - s . (3 . 10^{8} \frac{m}{s})}{(1.5) . 1.60 . 10^{- 19} J}$ ${ (6.62 . 10^-34) J-s .(3 . 10^8 m/s)} /{(1.5) . 1.60 . 10^-19 J}$

$λ = 827.5 n m$ $lambda = 827.5 nm$

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A semiconductor has a band gap of 1.5 eV. What is the minimum wavelength in nm required to promote an electron from the valence to the conduction band?

Not sure where to start :S

1 Answer

Explanation:

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