Charge carriers in doped semiconductors are

Analysis

The question asks for the identity of the charge carriers responsible for electrical conduction in doped semiconductors. To answer this, we need to understand how doping changes the electrical properties of intrinsic semiconductors like Silicon or Germanium.

Concept Explanation

In an intrinsic (pure) semiconductor, conduction is limited. Doping is the process of adding specific impurities to the semiconductor to increase its conductivity:

1. n-type doping: Adding pentavalent atoms (like Phosphorus) introduces extra electrons into the crystal lattice. These electrons become the majority charge carriers.
2. p-type doping: Adding trivalent atoms (like Boron) creates "vacancies" in the crystal lattice where an electron is missing. These vacancies are called holes. Holes act as positive charge carriers because electrons can move into them, effectively making the hole appear to move in the opposite direction.

Therefore, in any doped semiconductor, the current is carried by the movement of these two entities: free electrons and holes.

Step-by-Step Solution

1. Evaluate Option A: Protons are located in the nucleus of an atom and are not free to move through a crystal lattice to conduct electricity. This is incorrect.
2. Evaluate Option B: Neutrons have no charge and do not contribute to electrical conduction. This is incorrect.
3. Evaluate Option C: Anions and cations are ions found in electrolytes (liquids), not in solid-state semiconductors. This is incorrect.
4. Evaluate Option D: Electrons (negative charge carriers) and holes (positive charge carriers) are the fundamental particles that move through the lattice of a doped semiconductor to create current. This is correct.

Conclusion

Based on semiconductor physics, the charge carriers are indeed electrons and holes.

Exam Tip: Remember the mnemonic "n for negative (electrons)" and "p for positive (holes)". If you are ever confused, just remember that semiconductors are all about the interaction between the "sea" of electrons and the "vacancies" (holes) left behind!