What happens in reverse bias after a voltage breakdown ?

In a diode, reverse bias refers to applying a voltage across the diode such that the voltage is negative on the P-type semiconductor and positive on the N-type semiconductor. Under normal reverse bias conditions, a small leakage current may flow due to minority carriers in the semiconductor material. However, if the reverse bias voltage exceeds a critical value known as the breakdown voltage (also called the breakdown or breakdown voltage), significant changes occur in the diode’s behavior.

At the breakdown voltage in reverse bias, the electric field within the depletion region of the diode becomes strong enough to ionize the atoms in the semiconductor material. This phenomenon results in a sudden increase in current through the diode, often referred to as avalanche breakdown or Zener breakdown, depending on the diode’s construction and doping profile. During avalanche breakdown, carriers gain sufficient energy from the electric field to generate additional charge carriers through collision processes, causing a rapid increase in current flow through the diode.

If the reverse bias voltage exceeds the breakdown value of a diode, the current through the diode can escalate rapidly, potentially leading to damage or destruction of the diode due to overheating. This condition is undesirable in most circuit applications unless the diode is specifically designed to operate in breakdown mode, such as Zener diodes used for voltage regulation or protection circuits. Exceeding the breakdown voltage can cause the diode to conduct in reverse bias beyond its intended capacity, compromising its functionality and potentially affecting the entire circuit’s performance or safety.

After a breakdown in voltage, the behavior of the diode changes significantly. If the breakdown occurs in a controlled manner, such as in Zener diodes, the diode can maintain a relatively constant voltage across its terminals despite changes in current. However, if the breakdown is unintended or excessive, the diode may fail completely, leading to permanent damage or failure within the circuit. It’s crucial to ensure that diodes are operated within their specified voltage ratings to prevent breakdown under normal operating conditions and maintain the integrity and reliability of the electronic circuitry.

When a diode is reverse biased, the voltage across its terminals increases beyond the threshold at which significant current flows. Initially, under low reverse bias voltages, only a small leakage current flows due to minority carriers. However, as the reverse bias voltage increases towards the diode’s breakdown voltage, the current through the diode can increase dramatically due to avalanche or Zener breakdown mechanisms. This reverse current can potentially damage the diode or other components in the circuit if not appropriately managed or protected. Therefore, understanding the reverse bias characteristics and ensuring proper voltage limits are critical for maintaining the reliability and longevity of diodes in electronic circuits.

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