20 Physics -- Solids

Explain the formation of potential barrier and depletion region in p-n junction.

1 Answers

In a p-n junction, the formation of a potential barrier and depletion region occurs due to the diffusion of majority charge carriers. When a p-type semiconductor (with positive charge carriers, or "holes") is brought into contact with an n-type semiconductor (with negative charge carriers, or "electrons"), diffusion takes place. Electrons from the n-side diffuse towards the p-side, while holes from the p-side diffuse towards the n-side. This diffusion process continues until equilibrium is reached.

As a result, the n-side near the junction becomes positively charged, and the p-side near the junction becomes negatively charged. This charge separation creates an electric field, leading to the formation of a potential barrier, or built-in voltage, at the junction. The region surrounding this potential barrier is known as the depletion region. The depletion region is essentially devoid of mobile charge carriers, as the free electrons from the n-side combine with the holes from the p-side, creating an electrically neutral region with a fixed charge, or space charge region, across the junction.

A p-type semiconductor has a large number of holes but still, it is electrically neutral. Explain?

Ans: When the pure semiconductor (like Ge or Si) is doped with trivalent impurities (like Aluminium, Indium, Gallium, etc) only three electron of impurity element (Al) share with semi conductor atom (Si) leaving a hole. An P-type semiconductor has a large number of holes but still it is electrically neutral.

Explain how the P-type and N-type semiconductor are formed .

P-type and N-type semiconductors are formed through a process called doping. In P-type doping, impurities with fewer valence electrons than the semiconductor material, such as boron or gallium, are introduced, creating positively charged "holes" as the majority charge carriers. In N-type doping, impurities with more valence electrons, like phosphorus or arsenic, are added, resulting in an excess of negatively charged electrons as the majority charge carriers. Doping alters the electrical...

What is the difference between conductor and insulator?

Distinguish between Electrons and holes .

Electrons are negatively charged particles in atoms that carry current in conductors, whereas holes are vacant states in a semiconductor's valence band, which act like positively charged particles. Electrons move by gaining energy, while holes move by losing energy, resulting in opposite current flow directions.

What is meant by Fermi energy and Fermi energy level ?

Fermi energy refers to the highest energy level occupied by an electron at absolute zero temperature in a material. It is a concept from quantum mechanics and is named after the Italian physicist Enrico Fermi.

The Fermi energy level, also known as the Fermi level, is the energy level that separates filled electron states from empty states in a material. It serves as a reference point for describing the behavior of electrons in a material, particularly in metals and semiconductors. At absolute...

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