1 electron = 1 photon?

Started Apr 12, 2013 | Discussions thread
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Jack Hogan OP Veteran Member • Posts: 5,399
Re: 1 electron = 1 photon?

gvk wrote:

There is a good summary of the photoelectric effect in silicon in Chapter 2 of Janesick's book on photon transfer. From the band gap IR cutoff at 1.0868 um to 400 nm, covering near IR through visible spectrum, only a single conduction band electron is generated per photon absorbed. For photon energy greater than 3.1 eV (< 400 nm wavelength), the photoelectron produced can have enough energy to free additional electrons by collisions; 3.1eV is more than twice the Si band gap due to the momentum conservation condition with non-direct band gap semiconductor materials mentioned earlier in this thread. For photon energy above 10 eV, the average number of electrons generated by a single photon (quantum yield) is given by the photon energy (h nu) / 3.65 eV, where 3.65 eV is the energy required to generate an electon-hole pair in Si. Hard X-ray photons, above about 10 keV, have small collision cross sections with low probability for interaction with Si.

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Very good explanation, Gerry, it fits well with my gut feeling (which is not always a good thing :-)).  Janesick's book has come up in a number of discussions, I am going to have to get me a copy.

So, as it pertains to sensors in widely available modern DSLRs, can we assume that in practice multiple electron generation happens very seldom?

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