The working principle of the diode (conducting in the forward direction and non-conducting in the reverse direction)
A crystal diode is a pn junction formed by a p-type semiconductor and an n-type semiconductor. A space charge layer is formed on both sides of the interface, and a self-built electric field is built. When there is no applied voltage, because of the carriers on both sides of the pn junction The diffusion current caused by the concentration difference and the drift current caused by the self-built electric field are equal and in an electrical equilibrium state. When a forward voltage bias is generated, the mutual suppression of the external electric field and the self-built electric field increases the diffusion current of the carriers and causes the forward current (that is, the cause of conduction). When the reverse voltage bias is generated, the external electric field and the self-built electric field are further strengthened, forming a reverse saturation current I0 that has nothing to do with the reverse bias voltage in a certain reverse voltage range (this is the reason for non-conductivity).
When the applied reverse voltage is high to a certain level, the electric field strength in the space charge layer of the pn junction reaches a critical value, and the multiplication process of carriers is generated, a large number of electron-hole pairs are generated, and a large reverse breakdown current is generated. , Known as the breakdown phenomenon of the diode.


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