PN Junction – Semiconductor Electronics

PN Junction – Semiconductor electronics for class 12 physics students.

When P-Types and N-Types semiconductor are joined together such that crystal structure remains continuous, a p-n junction is formed. It is formed by adding excessive impurities to n-type semiconductor or donor impurities to a p-type semiconductor. When PN junction is formed, both material will find their fermilevels nonaligned. As diffusion takes place across the junction; the holes and electrons combine to neutralize each other at the junction and produce a free space called deflection layer. At the junction, due to migration of a few holes from p-types to n-types region, the negative immobile electrons are produced in P region and positive immobile ions are produced in N region. Under equilibrium, conducts a potential barrier is developed which prevents further diffusion.

Procedure:

• Connect the circuit with the diode forward biased.
• Switch on power supply.
• Increase voltage across diode in steps of 0.05v.
• Note the corresponding current ammeter.
• Record and tabulate the observation
• Plot V/I graph characteristics with voltage on x and current on y axis.
• Find slope and calculate dynamic resistance.

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