Semiconductor Electronics — Part 2: The p-n junction diode and rectifiers: visual lesson, CBSE Class 12 Physics

Lesson

The p-n junction diode

Part 2 — joining p-type and n-type silicon makes a one-way valve for current, and turns AC into DC.

In this lesson you will

Diagram

At the junction, electrons diffuse from n to p and holes from p to n, where they recombine.

This leaves a thin depletion layer with no mobile carriers, containing fixed negative acceptor ions (p side) and positive donor ions (n side).
These ions set up an electric field from n to p and a barrier potential (about 0.7 V for Si, 0.3 V for Ge) that opposes further diffusion.
Equilibrium: diffusion current (majority carriers) = drift current (minority carriers pushed by the field).

Check your understanding

Choose the correct option.

Multiple choice1 mark

The depletion layer of a p-n junction contains