How many free electrons are typically found in semiconductors?

In semiconductors, the typical number of free electrons available for conduction is four, which corresponds to the tetravalent nature of silicon and many other semiconductors used in electronic devices. Each silicon atom forms four covalent bonds with its neighbors by sharing its four valence electrons.

When silicon is thermally or optically excited, or when impurities (dopants) are introduced, some of these electrons can become free, allowing them to contribute to electrical conductivity. The presence of four valence electrons in the structure facilitates the formation of these bonds and the conduction process when conditions allow.

This characteristic enables semiconductors to have a unique balance between insulating and conducting properties, making them essential for various electronic components such as transistors and diodes.