Semiconductor physics

Which is the correct definition of the work function of a material?

  1. AThe energy difference between the vacuum level and the bottom of the conduction band
  2. BThe energy difference between the bottom of the conduction band and the top of the valence band
  3. CThe energy difference between the vacuum level and the Fermi level
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Answer: C. The energy difference between the vacuum level and the Fermi level

The work function is the energy needed to remove an electron at the Fermi level into vacuum, that is, the difference between the vacuum level and the Fermi level. In a semiconductor the Fermi level depends on the doping, so the work function changes too. The difference between the vacuum level and the bottom of the conduction band is the electron affinity.

  • A. The difference between the vacuum level and the conduction band bottom is the electron affinity.
  • B. The difference between the conduction band bottom and valence band top is the band gap.
  • C. Correct. The work function is the difference between the vacuum level and the Fermi level.
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More Semiconductor physics questions

  1. Which value is closest to the relative permittivity of silicon?
  2. Which value is closest to the electron mobility in lightly doped silicon at room temperature?
  3. In an indirect-gap semiconductor such as silicon, why is the probability of electron-hole recombination with light emission low?
  4. In a semiconductor driven out of thermal equilibrium by illumination or current injection, what are the levels introduced to describe the electron and hole densities separately?
  5. Which value is closest to the lattice constant of crystalline silicon?