Which diode, triode or FET will cause permanent damage after breakdown?
The breakdown of pn junction can be divided into avalanche breakdown, tunnel breakdown and thermoelectric breakdown.
The first two are generally not destructive. If the reverse voltage decreases immediately, the performance of pn junction can be restored. If the voltage is not lowered immediately, the pn junction will be destroyed. When a reverse voltage is applied to the pn junction, if there is no good heat dissipation condition, the junction temperature will rise and the reverse current will further increase. This cycle will be repeated, and finally the pn junction will break down. The breakdown caused by thermal instability is called thermoelectric breakdown, which is permanently destructive. The breakdown of pn junction is an important electrical property of pn junction. Breakdown voltage limits the working voltage of pn junction, so semiconductor devices have certain requirements for breakdown voltage. However, many devices such as Zener diode, avalanche diode and tunnel diode can be manufactured by using the breakdown phenomenon.
There are two physical mechanisms for reverse biased PN junction breakdown: Zener breakdown and avalanche breakdown. Zener breakdown will occur in heavily doped PN junction due to tunneling mechanism. In heavily doped PN junction, the conduction band and valence band on both sides are very close under reverse bias condition, so that electrons can tunnel directly from P region to N region.
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