Bandlückenkonzept

The Bandlückenkonzept, or band gap concept, is a fundamental principle in solid-state physics explaining the electrical properties of materials. It describes the energy difference between the valence band, where electrons are bound to atoms, and the conduction band, where electrons are free to move and conduct electricity. In metals, the valence and conduction bands overlap, meaning electrons can easily move into the conduction band, resulting in high conductivity. Insulators have a large band gap, so a significant amount of energy is required to excite electrons into the conduction band, making them poor conductors. Semiconductors possess a moderate band gap. At absolute zero temperature, they behave like insulators. However, with increasing temperature or the introduction of impurities (doping), electrons can gain enough energy to cross the band gap into the conduction band, allowing for controlled electrical conductivity. This ability to alter conductivity makes semiconductors crucial for electronic devices. The size of the band gap directly influences a material's optical properties as well, determining which wavelengths of light it absorbs or transmits.