Semiconductor physics

What is the energy difference between the vacuum level and the bottom of the conduction band of a semiconductor called?

  1. AElectron affinity
  2. BWork function
  3. CBand gap
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Answer: A. Electron affinity

The electron affinity (χ) is the energy needed to remove an electron from the bottom of the conduction band into vacuum, about 4.05 eV for silicon. It is a material constant and does not change with doping. The work function, by contrast, is the energy from the Fermi level to the vacuum level and does depend on doping. In a heterojunction between different semiconductors, the difference in electron affinity sets the conduction-band offset (ΔEc) (Anderson's rule).

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