Difference between intrinsic and extrinsic semiconductor.

Intrinsic and extrinsic semiconductors are two types of materials that exhibit intermediate electrical conductivity, in contrast to conductors and insulators. The main difference between intrinsic and extrinsic semiconductors lies in their level of impurity doping.

Intrinsic Semiconductor: An intrinsic semiconductor is a pure semiconductor material, typically silicon (Si) or germanium (Ge), with no intentional impurities added to it. It is characterized by a balanced number of electrons and holes, which are the charge carriers responsible for electrical conduction. Intrinsic semiconductors have a specific energy band structure, consisting of a valence band and a conduction band separated by a bandgap. At absolute zero temperature, all electrons are in the valence band, and the material behaves as an insulator. However, at higher temperatures or with the application of energy, some electrons can be excited to the conduction band, resulting in a finite electrical conductivity.


Extrinsic Semiconductor: An extrinsic semiconductor is a semiconductor material doped with impurities intentionally added to alter its electrical properties. Impurity atoms from Group III or Group V elements are added to the pure semiconductor crystal lattice, creating either p-type or n-type semiconductors.

P-type Semiconductor: In p-type semiconductors, impurity atoms from Group III elements, such as boron (B), are added. These impurity atoms have fewer valence electrons than the atoms of the pure semiconductor material. Consequently, they create "holes" in the valence band, which act as positive charge carriers. The majority charge carriers in a p-type semiconductor are holes, and the electrical conductivity is predominantly due to the movement of holes.


N-type Semiconductor: In n-type semiconductors, impurity atoms from Group V elements, such as phosphorus (P), are added. These impurity atoms have more valence electrons than the atoms of the pure semiconductor material. As a result, they introduce additional free electrons into the conduction band, which act as negative charge carriers. The majority charge carriers in an n-type semiconductor are electrons, and the electrical conductivity is predominantly due to the movement of electrons.

By intentionally doping intrinsic semiconductors with appropriate impurities, the electrical conductivity and other characteristics of the resulting extrinsic semiconductors can be modified for specific applications. This is the basis for many electronic devices, such as diodes, transistors, and integrated circuits.