p-n Junction

Depletion region forms at the interface.

Concept

p-n Junction is a foundational idea in this chapter. The defining relationship is:

$V_b = (kT/e)\ln(N_A N_D/n_i^2)$

Built-in potential ~0.6–0.7 V for Si, ~0.3 V for Ge.

Worked Application

Apply the formula to a typical problem from your textbook. Identify the knowns, plug into the equation, and check that the units work out. Always sanity-check the magnitude before accepting an answer.

Common Confusions

• Confusing the variables in the formula — re-read the symbol definitions in the chapter.
• Forgetting unit conversions (cm vs m, g vs kg).
• Ignoring sign conventions where direction matters.

Key Takeaways

• Master the formula $V_b = (kT/e)\ln(N_A N_D/n_i^2)$ and one canonical example.
• See the chapter index for full derivations, traps and exam-grade problems.