NEETPhysicsSemiconductors
The I - V characteristic of a heavily doped p - n junction diode can be divided into three distinct regions: region P (forward bias curve), region Q (reverse bias curve with negligible current), and region R (sharp vertical drop in the reverse bias curve). In which region is the diode operated as a voltage regulator, and what is the underlying physical reason for the sharp increase in current in this region?
Options
- ARegion R ; due to a very high electric field across an extremely thin depletion region tearing electrons from
- BRegion R ; due to a very wide depletion region where minority carriers gain high kinetic energy and cause aval
- CRegion Q ; due to the steady injection of minority carriers across the junction under reverse bias.
- DRegion P ; due to a low barrier potential resulting from the heavy doping of the p and n sides.
Correct answer
A. Region R ; due to a very high electric field across an extremely thin depletion region tearing electrons from
Step-by-step solution
A Zener diode is a heavily doped p - n junction diode designed to operate in the reverse breakdown region (region R ). Because of heavy doping, the depletion region is extremely thin (of the order of This high electric field is strong enough to pull valence electrons from their host atoms, generating a large number of electron-hole pairs and causing a sharp increase in current. This phenomenon is known as internal field emission or Zener breakdown. Region P represents forward bias, and region Q represents the pre-b