How can thermal energy create free electrons and holes in a semiconductor?

In a semiconductor, thermal energy facilitates the creation of free electrons and holes through the process of thermal vibration.12

At low temperatures, electrons in a semiconductor are bound within the crystal structure, typically occupying the valence band. As the temperature increases, thermal vibrations provide sufficient energy to break some of the covalent bonds that hold the crystal together.12

When a bond is broken, an electron gains enough thermal energy to cross the energy gap (bandgap) and move into the conduction band, becoming a free electron capable of participating in electrical conduction. The departure of this electron leaves behind an electron deficiency in the valence band, which is referred to as a hole. This hole acts as a positively charged mobile carrier. Together, these thermally generated charge carriers—the free electron and the hole—form an electron-hole pair that allows the material to conduct electricity.123