An impurity in semiconductors is a foreign element that is intentionally added to the crystal structure of silicon or germanium. These impurities are also known as dopants and are used to alter the electrical properties of the semiconductor.
Impurities are added to semiconductors in order to create more free electrons or holes, which are necessary for the conduction of electricity. This process is known as doping and is essential for the functionality of semiconductor devices.
The most commonly used impurities in semiconductors are boron, phosphorus, arsenic, and antimony. These elements are from group III and group V of the periodic table and are known as p-type and n-type dopants, respectively.
The addition of impurities can either increase or decrease the conductivity of semiconductors, depending on the type of dopant used. P-type dopants create holes in the valence band, making the material more conductive, while n-type dopants create free electrons in the conduction band, also increasing conductivity.
The addition of impurities in semiconductors allows for the creation of different types of transistors, diodes, and other electronic devices. This technology is essential for modern technology and is used in a wide range of applications, including computers, smartphones, and solar cells.