Semiconductor physics

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?

  1. ADonor levels
  2. BQuasi-Fermi levels
  3. CThe intrinsic Fermi level
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Answer: B. Quasi-Fermi levels

Out of equilibrium, a single Fermi level can no longer describe both the electron and hole densities. Separate quasi-Fermi levels (imrefs) are therefore introduced for electrons and holes. The difference between them relates to quantities such as the open-circuit voltage of a solar cell.

  • A. Donor levels are levels near the conduction band created by donor impurities.
  • B. Correct. Out of equilibrium, separate quasi-Fermi levels are used for electrons and holes.
  • C. The intrinsic Fermi level is the Fermi level of an intrinsic semiconductor, located near mid-gap.
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More Semiconductor physics questions

  1. Which value is closest to the lattice constant of crystalline silicon?
  2. Why is the intrinsic Fermi level of silicon slightly offset from the exact center of the band gap?
  3. Which value is closest to the band gap of silicon (Si) at room temperature?
  4. Which statement is correct when phosphorus (P) is added to silicon as an impurity?
  5. What happens to the intrinsic carrier density when the temperature of an intrinsic semiconductor is raised?