Concept:Pentavalent impurity atoms (Group V, such as P, As, Sb) have five valence electrons. Four participate in covalent bonding with the host lattice while the fifth is donated to the conduction band, forming an N-type semiconductor.
Formula:$$\text{Group V Dopant (P)} + \text{Group IV Host (Si)} \implies \text{N-type Semiconductor } (n \approx N_D \gg p)$$
Solution:- Phosphorus has 5 valence electrons. Four bond covalently with adjacent silicon atoms.
- The fifth electron is loosely bound and easily excited into the conduction band at room temperature, making electrons the majority carriers in an N-type material.
Why other options are incorrect:- Option A: P-type semiconductors are formed by doping with trivalent Group III elements.
- Option B: Doping silicon produces an extrinsic semiconductor, not a superconductor.
- Option C: Doping increases semiconductor conductivity rather than creating an insulator.
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