Break down voltage of a diode is \(5 \mathrm{~V}\). By which effect this breakdown occurs in diode? (A) Only avalanche effect (B) Only zener effect (C) Avalanche or zener effect (D) None of the above

The avalanche effect and zener effect are two primary mechanisms for the breakdown of diodes. Avalanche effect occurs when the electric field across the depletion region becomes so strong that it accelerates the free electrons to the point where, upon colliding with the semiconductor's atoms, they cause secondary ionizations, producing more free carriers. This results in a sudden rise in current, leading to an avalanche of free electrons. Avalanche effect usually occurs when breakdown voltage is above 6V. Zener effect, on the other hand, occurs typically in heavily doped semiconductors with breakdown voltage lower than 6V. A strong electric field across the depletion region can cause a significant number of valence electrons to "tunnel" from the valence band to the conduction band, creating a pronounced increase in current flow.

We are given that the breakdown voltage of the diode is 5V. Since the zener effect occurs when the breakdown voltage is lower than 6V, we can infer that the breakdown in this case might be due to the zener effect.

Based on the given information and our analysis, we can determine that the breakdown in this case is most likely due to the zener effect. Therefore, the correct option is: (B) Only zener effect