1 electron = 1 photon?

Started Apr 12, 2013 | Discussions thread
Carl Decker Regular Member • Posts: 133
In short: WE usually currently do get only one electron ?

alanr0 wrote:

If the photon has sufficient energy, more than one electron can be released.  PhotonTrapper has identified possible mechanisms, such as double electron photoemission.  I don't believe this or other mechanisms make a significant contribution when conventional silicon photodiodes exposed to visible light.

At much higher (X- and gamma-ray) photon energies, Compton scattering can release multiple electrons as a photon propagates through the material.  At each scattering event, an electron-hole pair is created, and the photon loses some energy.  Consult Storm & Israel's tables for the dependence on atomic number and photon energy if you don't have access to code like this.

A different mechanism operates in an avalanche photodiode (APD).  Arguably there are two processes operating sequentially here.  An electron-hole pair is first generated by photo-absorption.  APDs operate at much higher bias voltages than conventional photodiodes, and the carriers are accelerated by the bias field, releasing further electron-hole pairs by avalanche multiplication.

Impact ionisation is also exploited by electron-multiplying EMCCD detectors, to produce multiple electrons from a single absorbed photon.


I also try to read it without going to much into depth, summary:

There exists a possible mechanism which does not have a significant contribution in conventional silicon photodiodes ( we use ).

There also exist gamma rays ( we photographers do not use ) and special sensors ( we photographers do not use ) to produce several electrons.

So the practical conclusion is: currently usually only one electron per photon, or less.

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