Question

Write the two processes that take place in the formation of a p-n junction. Explain with the help of a diagram, the formation of depletion region and barrier potential in a p-n junction.

Answer 1

1) AVALANCHE BREAKDOWN:

1. It takes place in thicker junction.
2. In this mechanism, when electric field existing in the depletion layer is sufficiently high the velocity of the carriers (minority carriers) colloid with the crystal atoms, thus creating electron-hole pairs.

As, pair of electron-hole is created in the midest of high field, they quickly separate and attain high velocity to cause further pair generation. So, that chain of collisions can give rise to an almost infinite current with very slight additional increase in voltage . This process is known as AVALANCHE BREAKDOWN .

2) ZENER BREAKDOWN:

1. It takes place in very thin junction.
2. With small applied reverse voltage, it becomes possible for electrons to jump across barrier from valence band. In p material to some of the unfilled conduction band n material. This process is known as ZENER BREAKDOWN.