Concept:Diffusion of mobile carriers across the junction exposes uncompensated donor ions (positive) on the N-side and uncompensated acceptor ions (negative) on the P-side.
Formula:$$\text{N-side Space Charge: } +q N_D \quad | \quad \text{P-side Space Charge: } -q N_A$$
Solution:- Free electrons diffuse from the N-side into the P-side, leaving behind fixed, ionized positive donor atoms (\( N_D^+ \)).
- Holes diffuse from the P-side into the N-side, leaving behind fixed, ionized negative acceptor atoms (\( N_A^- \)).
- Thus, the depletion layer carries net positive charge on the N-side and net negative charge on the P-side.
Why other options are incorrect:- Option A: This reverses the space-charge polarity across the junction.
- Option B: Positive charge on both sides would violate overall crystal electrical neutrality.
- Option C: Negative charge on both sides would violate charge neutrality.
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