What happens to germanium or silicon when doped with impurities?

When germanium or silicon is doped with impurities, they become conductors. This process involves introducing specific types of impurity atoms into the semiconductor material to enhance its electrical conductivity. Depending on the type of dopant used, either n-type or p-type semiconductors are formed.

In n-type doping, elements that have more valence electrons than silicon or germanium—such as phosphorus or arsenic—are added. These extra electrons increase the number of charge carriers, thus enhancing the material's ability to conduct electricity. Conversely, p-type doping involves adding elements with fewer valence electrons, such as boron, creating "holes" that also contribute to conductivity.

The doping process modifies the electronic structure of the semiconductor, significantly increasing its conductivity compared to the pure (intrinsic) form. This characteristic is fundamental for creating various electronic components, like diodes and transistors, which are essential in modern electronics.