PHYSICS

JAMB 2003 - Question 47

Physics 2003 JAMB Past Questions - Question 47: In a semiconductor junction diode, as the depletion or barrier layer is forward-biased, the layer

Choose the correct answers from the options given.
In a semiconductor junction diode, as the depletion or barrier layer is forward-biased, the layer
A:
B:
C:
D:
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Correct Answer

C

Explanation

In a semiconductor junction diode, when the depletion or barrier layer is forward-biased, several important changes occur within the diode structure:

1. Reduction in the Barrier Width: The barrier layer, also known as the depletion region, narrows as the diode is forward-biased. This is because the applied voltage creates an electric field that pushes the charge carriers (electrons and holes) away from the junction, reducing the width of the depletion region.

2. Conduction of Current: With the narrowing of the depletion region, charge carriers are able to move across the junction more easily. Electrons from the n-type region and holes from the p-type region are attracted towards the junction and can combine, allowing current to flow through the diode.

3. Lower Resistance: As the depletion region narrows, the resistance across the diode decreases. This is because the electric field that initially prevented charge carriers from moving through the junction is now weakened, and the diode exhibits a lower resistance to the flow of current.

4. Emitting Light (in case of LEDs): If the diode is designed as a light-emitting diode (LED), the forward-biasing can cause the recombination of electrons and holes in the semiconductor material, resulting in the emission of photons and the generation of light.

5. Temperature Dependence: It's important to note that the forward-biasing of a diode causes an increase in its temperature due to power dissipation. This change in temperature can impact the diode's electrical characteristics and, in some cases, it may lead to thermal runaway if not properly controlled.

Overall, forward-biasing a semiconductor junction diode allows it to conduct current in the forward direction by reducing the barrier or depletion layer's width and enabling the flow of charge carriers across the junction. This behavior is a fundamental principle in the operation of diodes in electronic circuits.