A pure semiconductor at absolute zero temperature behaves as

1. At 0 K, the valence band of a pure semiconductor is full and the conduction band is empty. 2. No charge carriers exist for current flow without thermal excitation. 3. Hence it acts as a perfect insulator at 0 K, becoming conductive only on heating or doping. _Source: Maharashtra Balbharati Std XII Chemistry, Ch 1 "Solid State" §1.12_