The pn‐Junction

This chapter explains how a juxtaposition of one p- and one n-type semiconductor creates a pn-junction or a semiconductor diode, a device that lets the current go in just one direction. The combination of two different types of semiconductors, p and n, creates a pn-junction and generates a transition region which creates an internal electrical voltage. In equilibrium, the diffusion current due to the difference of electrons and holes densitycancels the drift current due to this intrinsic electric field so the current outside the diode. The chapter also discusses two variations of the diode. The Schottky diode replaces one of the semiconductors by a metal, making it a faster and lower power diode. The tunnel diode, which can be explained only in terms of quantum mechanics, has a large reverse bias current and also results in a region of negative resistance.