The "reverse breakdown region" in a diode's current-voltage (I-V) characteristic refers to a specific operating condition where the diode is subjected to a reverse voltage (negative voltage) that exceeds a critical value known as the "reverse breakdown voltage" or "peak inverse voltage" (PIV). When the reverse voltage across the diode reaches or exceeds this critical value, the diode enters the reverse breakdown region, and a phenomenon called "avalanche breakdown" or "Zener breakdown" occurs.
In the reverse breakdown region, the diode exhibits a sudden and significant increase in current flow, even though the voltage remains reverse-biased. This sharp increase in current happens because the reverse-biased electric field becomes strong enough to generate electron-hole pairs through a process called impact ionization. These newly generated carriers, in turn, create more carriers, leading to a chain reaction that causes a rapid increase in current.
The reverse breakdown region is typically undesirable in standard diode applications, as it can lead to device failure due to excessive current flow and overheating. However, certain specialized diodes, like Zener diodes and avalanche diodes, are designed to operate in this region intentionally and are utilized in voltage regulation and protection circuits.
It is essential to use diodes with reverse breakdown voltage ratings suitable for the specific application to avoid accidental breakdown and ensure reliable performance.