Depletion Layers in pn junction

In summary, heavily doped pn junctions have a quicker formation of the electric field that prevents further diffusion of holes and electrons, due to the quicker recombination of charges near the junction, resulting in narrower depletion layers compared to less heavily doped pn junctions.
  • #1
*FaerieLight*
43
0
Hi,

Can someone please tell me if it is true that in heavily doped pn junctions, the electric field that prevents further diffusion of holes and electrons is set up more quickly than in less heavily doped pn junctions? Is this essentially because the holes and electrons recombine more quickly and very near the join between the p and n type semiconductors, which occurs because the charges don't need to travel very far before they recombine?
So then is this the reason why depletion layers for such pn junctions are narrower than for less heavily doped pn junctions?

Thanks a lot.
 
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  • #2
*FaerieLight* said:
Hi,

Can someone please tell me if it is true that in heavily doped pn junctions, the electric field that prevents further diffusion of holes and electrons is set up more quickly than in less heavily doped pn junctions? Is this essentially because the holes and electrons recombine more quickly and very near the join between the p and n type semiconductors, which occurs because the charges don't need to travel very far before they recombine?
So then is this the reason why depletion layers for such pn junctions are narrower than for less heavily doped pn junctions?

Thanks a lot.
Actually, In heavily doped P-N junction there are lot of donor (+ive charge) and accepters (-ive charge) in n and p region respectively. when junction is formed the electron from n side to p side to recombine with holes and vice versa, leaving behind -ive donor in n region and +ive acceptors in p region. Theses +ive and -ive charges setup an internal Electric filed Ein which prevent the further diffusion of charge carriers(electron and holes).. So in the case of heavily doped of p-n junction, only less recombination of electron and holes is required to set up the Electric field which prevent the further diffusion, resulting in narrow depletion region... while is lightly doped large no. recombination of electron and holes is required which result in wide band gap.
 

1. What is a depletion layer in a pn junction?

A depletion layer is a region of a semiconductor material where there is a lack of mobile charge carriers. This is typically found in a pn junction, which is the interface between two regions of a semiconductor material with different levels of doping, creating a built-in electric field.

2. How is a depletion layer formed in a pn junction?

A depletion layer is formed when electrons from the n-doped region diffuse into the p-doped region and combine with holes, leaving behind positively charged ions in the n-doped region and negatively charged ions in the p-doped region. This creates an electric field that prevents further diffusion of charge carriers.

3. What is the significance of a depletion layer in a pn junction?

The depletion layer plays a crucial role in the functioning of a pn junction. It acts as a barrier, preventing current flow in the reverse biased direction and allowing current flow in the forward biased direction. This makes it a key component in many electronic devices, such as diodes and transistors.

4. How does the width of the depletion layer change with applied voltage?

The width of the depletion layer is directly proportional to the applied voltage. As the voltage increases in the forward biased direction, the depletion layer becomes thinner, allowing for more current flow. In the reverse biased direction, the depletion layer widens, restricting current flow.

5. What happens to the depletion layer at the junction when a pn junction is formed?

At the junction of a pn junction, the depletion layer is at its widest point. This is where the majority of the built-in electric field is located, as the two regions with different doping levels come together. This electric field is what creates the barrier and controls the flow of current in the pn junction.

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