NEETPhysicsSemiconductors
A heavily doped p - n junction diode undergoes Zener breakdown at a reverse bias voltage of 5 V . Which of the following correctly explains the primary mechanism responsible for this breakdown?
Options
- AMinority carriers gain high kinetic energy from the electric field and break covalent bonds through collisions
- BA very high electric field across the thin depletion region directly pulls electrons from covalent bonds.
- CThe wide depletion region generates excessive heat under reverse bias, causing thermal breakdown of the juncti
- DMajority carriers easily cross the junction due to a significant decrease in the barrier potential under rever
Correct answer
B. A very high electric field across the thin depletion region directly pulls electrons from covalent bonds.
Step-by-step solution
Zener breakdown occurs in heavily doped p - n junction diodes. Heavy doping results in a very thin depletion region. Even at a relatively low reverse bias voltage (like 5 V ), the electric field across the extremely thin depletion region becomes very high ( E = V/d ). This intense electric field is sufficient to directly pull electrons out of covalent bonds, creating a large number of electron-hole pairs. This process is known as internal field emission. Option 1 describes avalanche breakdown, which occurs in light