Glossary

Depletion region

Beginner

A thin empty zone with almost no free electrons or holes, where they have been pushed away or used up.

Novice

A region swept clear of mobile carriers, leaving the fixed, charged dopant atoms behind. Their charge creates the electric field across a p-n junction and under a MOS gate. It acts as an insulator, so it behaves like the gap in a capacitor.

Expert

Width W=2εsV/(qN)W = \sqrt{2\varepsilon_{\mathrm{s}} V/(qN)} for a one-sided junction, with VV the total potential across it and NN the lighter doping. Junction capacitance is εsA/W\varepsilon_{\mathrm{s}} A/W; under a MOS gate WW saturates at WdmaxW_{\mathrm{dmax}} once the surface inverts.

Explained in Bands, doping and the p-n junction (Transistors).

See also: Built-in potential (φbi), p-n junction.

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