1. Home
  2. Lectures

Energy for charge carrier generation in semiconductor material

  1. 01 June 2012

 

The energy W required to create an e-h pair in a semiconductor by a charged mass particle traversing the medium depends on the band gap energy Eg of the material and hence, although only slightly, on the temperature.

The measurements of this quantity show a nearly linear dependence on the band gap energy, and the linear fit to the data obtained for different materials gives [1]

The energy for charge carrier generation is always higher than the band gap energy due to the possible additional excitation of phonon and plasmon states. Phonon excitation transfers energy to the lattice, and the energy transferred appears finally as heat in the detector.

The plasmon is the quantum of the valence electron density oscillations with a mean energy of 17 eV for silicon. The valence electrons are those of the M-shell and they are only weakly bound to the atoms. Thus, they may be considered as a dense and nearly homogeneous density gas, i.e. plasma of negative charge carriers in the semiconductor material volume.

The mean energy W  to create an e-h pair has been calculated and measured in experiments including high  energy charged particles and X-ray photons [1,2]. The mean energy W required to create an e-h pair in silicon is W ≈ 3.68 eV.

References

  1. R.C.Alig, S.Bloom, C.W.Struck, Scattering by Ionization an Phonon Emission In Semiconductors, Phys. Rev. B, Vol.22, No.12, (1980), pp.5565-5582.
  2. G.W.Fraser et al., The X-ray Energy Response of Silicon, Nucl. Instr. and Meth., A 350, (1994), pp.368-378.

If you like... share with your friends