Physics · Semiconductor Electronics : Materials, Devices And Simple Circuits · NEET
No. Electrons are majority only in n-type semiconductors. In a p-type semiconductor, holes are the majority carriers and electrons are the minority carriers. So you must first check the type. The rule is simple: n-type -> electrons are majority; p-type -> holes are majority. Do not assume electrons win everywhere just because they carry the current in metals.
Holes are the majority carriers in a p-type semiconductor. A p-type is made by doping silicon or germanium with a trivalent atom (like boron, aluminium, indium). Each trivalent atom is short of one electron, so it creates a hole. These extra holes are far more than the few thermally-made electrons, so nh >> ne. The holes are majority; the electrons are minority.
In reverse bias, the battery pushes the majority carriers away from the junction, so they cannot cross. But minority carriers (electrons in p-side, holes in n-side) are pushed toward the junction by the same field and do cross. That is why the small reverse current (in microamperes) is carried by minority carriers, not majority. This is a very common NEET trap. Since minority carriers are made by heat, this reverse current also grows when temperature rises.
Doping mainly creates majority carriers. For example, pentavalent doping adds free electrons (majority in n-type). The minority carriers are still made by thermal generation, the same process that happens in the pure crystal. Doping does not add minority carriers; in fact it lowers their number because of the mass action law (ne x nh = ni squared). Adding more electrons pushes the hole count down.
No. In a pure (intrinsic) semiconductor, electrons and holes are made in equal pairs, so ne = nh = ni. Neither is in the majority. The idea of majority and minority carriers only starts once you dope the crystal and make it extrinsic (n-type or p-type). So the terms majority and minority apply to extrinsic semiconductors only.
For a p-type semiconductor, which of the following statements is true?
Consider the following statements A and B and identify the correct answer: A. For a solar cell, the I-V characteristic lies in the IV (fourth) quadrant of the given graph. B. In a reverse biased p-n junction diode, the current measured in microampere is due to majority charge carriers.
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Majority carriers are the charge carriers present in large numbers in a doped semiconductor; minority carriers are the ones present in small numbers. In n-type they are electrons (majority) and holes (minority); in p-type they are holes (majority) and electrons (minority).
n-type is made by doping with a pentavalent atom (like phosphorus or arsenic). Each such atom gives one extra free electron. These donated electrons far outnumber the few thermally-created holes, so ne >> nh and electrons become the majority carriers.
Minority carriers are produced by thermal generation, the breaking of covalent bonds by heat. This is the same pair-making process as in a pure crystal. Because they depend on temperature, the minority carrier count rises when the semiconductor is heated.
ne >> nh means the electron concentration is much greater than the hole concentration. It is the defining condition of an n-type semiconductor, where electrons are majority and holes are minority. For p-type the reverse holds: nh >> ne.
Yes. Their product is fixed: ne x nh = ni squared, where ni is the intrinsic concentration. So if doping raises the majority count, the minority count falls to keep the product constant. This is why minority carriers are so few in a heavily doped semiconductor.
