Working principle and category of crystal diodes 2

Working principle of diode

A crystal diode is a p-n junction formed by p-type and n-type semiconductors, with space charge layers on both sides of its interface and a self built electric field. When there is no external voltage, the diffusion current caused by the difference in carrier concentration on both sides of the p-n junction and the drift current caused by the self built electric field are equal and in an electric equilibrium state.

When there is a forward voltage bias from the outside, the mutual suppression effect of the external electric field and the self built electric field increases the diffusion current of carriers, causing a forward current.

When there is a reverse voltage bias from the outside, the external electric field and the self built electric field are further strengthened, forming a reverse saturation current I0 that is independent of the reverse bias voltage value within a certain range of reverse voltage.diode

When the applied reverse voltage reaches a certain level, the electric field strength in the p-n junction space charge layer reaches a critical value, causing a doubling process of charge carriers and generating a large number of electron hole pairs, resulting in a significant reverse breakdown current, known as the diode breakdown phenomenon.

The conductivity characteristics of diodes

The most important characteristic of a diode is its unidirectional conductivity. In a circuit, current can only flow in from the positive pole of a diode and out from the negative pole. Below, we will demonstrate the forward and reverse characteristics of a diode through a simple experiment.diode