Concept:Pentavalent impurity atoms (donors like P, As, Sb) provide extra valence electrons that enter the conduction band, making electrons the predominant mobile charge carriers.
Formula:$$n \approx N_D \gg p$$
Solution:- Each pentavalent atom donates one conduction electron while leaving behind a fixed positive donor ion.
- Thermal generation creates a few electron-hole pairs, meaning electrons are the majority carriers and holes are the minority carriers.
Why other options are incorrect:- Option A: In N-type materials, electrons are the majority carriers and donor ions are positively charged.
- Option C: Equal concentrations (\( n = p = n_i \)) only occur in pure intrinsic semiconductors.
- Option D: Conduction in N-type material is dominated by free electrons.
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