# Why does carrier density change linearly over the depletion region?

The Feynman Lectures on Physics vol III, section 14-4 shows the following for a pn junction (a), with (b) representing potential and (c) representing carrier density:

Why does the carrier density vary as shown in (c)? Images of the depletion region show a negative charge associated with the p-type side of the region, and a positive charge associated with the n-type side, so surely there should be a greater electron density in the p-type side of the region and a greater hole density in the n-type side?

• The actual shape depends on the doping profiles in the $n$ and $p$ regions. What you have shown is a simple didactic representation - don't read too much into it. Oct 22, 2019 at 17:22