p-n junction: definition · Chip Field Guide

Beginner

The border where p-type and n-type silicon meet. It lets electricity through one way and blocks it the other way.

Novice

The interface between p-type and n-type regions. Carriers diffuse across, leaving a depletion region and a built-in voltage. Forward bias (p positive) lowers the barrier and current rises exponentially; reverse bias raises it and only a tiny leakage flows. Every source and drain in a MOSFET forms one with the body.

Expert

Ideal current $I = I_{0}(e^{qV/kT} - 1)$ with $I_{0} = Aqn_{\mathrm{i}}^2\,(D_{\mathrm{p}}/(L_{\mathrm{p}} N_{\mathrm{d}}) + D_{\mathrm{n}}/(L_{\mathrm{n}} N_{\mathrm{a}}))$ . Real junctions add generation-recombination current, series resistance, high-injection effects and avalanche or tunneling breakdown.