Concept:Doping introduces equal amounts of positive nuclear charges and negative atomic electrons. While pentavalent dopants create free conduction electrons, each free electron leaves behind a stationary positive donor ion (\(\text{P}^+\)) in the lattice, maintaining overall electrical neutrality.
Formula:$$q_{\text{total}} = q_{\text{electrons}} + q_{\text{holes}} + q_{\text{donor ions}} + q_{\text{acceptor ions}} = 0$$
Solution:- Before doping, both the host crystal and the impurity atoms are electrically neutral.
- When pentavalent atoms replace host atoms in the lattice, the total number of protons in the material still equals the total number of electrons.
- Therefore, the bulk semiconductor remains completely electrically neutral.
Why other options are incorrect:- Option A: Free electrons are balanced by fixed positive donor cores; the crystal is not negatively charged.
- Option B: Fixed donor ions are balanced by free conduction electrons; the crystal is not positively charged.
- Option D: Extrinsic semiconductors conduct current via mobile carriers and are not non-conducting dielectrics.
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