Number of electron-hole pairs produced by each photon in depleted silicon What is the distribution of the number of electron-hole pairs produced by a single photon in depleted silicon? Can you point me to bibliography on this?
I am currently interested in 1064 nm photons which have an energy of 1.165 eV. Knowing that the band gap energy of silicon is about 1.1 eV I would say that each photon produces just a single e-h pair, because the energy of the products (the e and the h) is very small (1.16 eV - 1.1 eV = 0.05 eV) to produce further pairs. This simplistic analysis does not take into account thermal fluctuations, and maybe a single e-h pair can be created with higher energy and produce another pair...
 A: In order to produce an electron-hole pair in an undoped semiconductor one needs to excite an electron from the valence band to the conduction band, i.e., across the gap. Thus, the energy of a photon is distributed as
$$
\hbar\Omega = E_g + \frac{\hbar^2 k_e^2}{2m_e} + \frac{\hbar^2 k_h^2}{2m_h},
$$
where $k_{e,h}$ are the momenta of the electron and the hole, and $m_{e,h}$ are their effective masses (i.e., the effective masses in the conductiona nd the valence bands. If $\hbar\Omega -E_g \ll E_g$, it is energetically impossible to create more than one electron-hole pair from a photon.
At non-zero temperature there will be certainly some electron-hole pairs already present, but these are not excited by the photon in question (although they might have been previously excited by thermal photons).
A caveat is that typical effective mass description of semiconductor material treats it as a collection of non-interacting electrons. This is not true and a free electron in the conduction band (or free hole in the valence band) is actually a collective motion of many electrons (holes). But in terms of these free quasiparticles there is still only one electron-hole pair.
