At absolute zero temperature ( 0 Kelvin), there is no thermal energy available. Semiconductors and Energy Bands: In a semiconductor, electrons reside in the valence band at lower energy levels. For conduction to occur, electrons need to jump from the valence band to the conduction band, leaving behind holes in the valence band. The energy required for this jump is called the band gap energy. Effect of Temperature: At typical room temperatures, some electrons gain enough thermal energy to cross the band gap and move into the conduction band, contributing to electrical conductivity. As temperature decreases, the number of thermally excited electrons decreases. At absolute zero temperature (0K), there is no thermal energy. Therefore, no electrons can gain enough energy to jump from the valence band to the conduction band. Result: The valence band remains completely filled. The conduction band remains completely empty. A material with a completely filled valence band and an empty conduction band, separated by a band gap, behaves as an insulator. There are no free charge carriers available for conduction. Therefore, at absolute zero temperature, a semiconductor behaves like an insulator.