N-type semiconductor is obtained when silicon or germanium is doped by Phosphorus.

Doping in Semiconductors:
Doping is a process of intentionally introducing impurities into a semiconductor material to modify its electrical properties. By doping, we can either increase the number of free electrons or increase the number of holes in the semiconductor material.

N-type Semiconductor:
N-type semiconductor is a type of semiconductor material where the majority charge carriers are negatively charged electrons. It is achieved by doping a pure semiconductor material, such as silicon or germanium, with impurities that have more valence electrons than the semiconductor material.

Doping with Phosphorus:
Phosphorus is a group V element in the periodic table and has five valence electrons. When it is introduced as an impurity in a silicon or germanium crystal lattice, it creates an excess of electrons. This is because phosphorus has one extra electron compared to silicon or germanium, which it can freely contribute to the crystal lattice.

Process of N-type Doping:
The process of N-type doping involves adding a small amount of phosphorus atoms to the silicon or germanium crystal lattice. This is typically done by introducing phosphorus atoms during the crystal growth process or by diffusing phosphorus atoms into the crystal lattice.

- The phosphorus atoms replace some of the silicon or germanium atoms in the crystal lattice.
- Since phosphorus has one extra valence electron, it contributes an excess of negatively charged electrons to the crystal lattice.
- These excess electrons become the majority charge carriers in the N-type semiconductor material.

Working of N-type Semiconductor:
In an N-type semiconductor, the excess electrons provided by the phosphorus atoms are free to move throughout the crystal lattice, making it a good conductor of electricity. When a voltage is applied across an N-type semiconductor, the majority electrons flow from the negative terminal to the positive terminal, creating an electric current.

Conclusion:
N-type semiconductors are obtained by doping silicon or germanium with impurities that have more valence electrons than the semiconductor material. Phosphorus is a commonly used impurity for N-type doping as it contributes an excess of electrons to the crystal lattice, making it a good conductor of electricity.