Concept:Doping introduces neutral impurity atoms into a neutral host crystal. Because the total number of protons equals the total number of electrons throughout the material, the entire crystal remains electrically neutral.
Formula:$$\text{Charge Neutrality Equation: } q(p + N_D^+) = q(n + N_A^-) \implies Q_{\text{net}} = 0$$
Solution:- In N-type material, every free electron is balanced by a bound positive charge in the donor nucleus (\( N_D^+ \)).
- In P-type material, every hole is balanced by a negative acceptor ion (\( N_A^- \)).
- Therefore, both N-type and P-type semiconductors are strictly electrically neutral.
Why other options are incorrect:- Option A: Confuses mobile carrier majority types with the net charge of the bulk crystal.
- Option B: Confuses fixed ion signs with the bulk crystal charge.
- Option D: Semiconductor crystals do not possess a net static charge.
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