What happens to resistivity of a semiconductor when temperature is raised?

Semiconductors behave in a completely opposite way to metals when it comes to temperature and resistivity — and this is one of the most important distinctions every Physics and Chemistry student must clearly understand. In metals, resistivity increases with temperature, but in semiconductors, raising the temperature actually decreases resistivity. The reason lies in how semiconductors generate charge carriers. At room temperature, very few electrons have enough energy to move freely, but as temperature rises, more and more electrons break free from their covalent bonds and become available for conduction — dramatically increasing the number of charge carriers and reducing resistivity.

• Charge carriers: as temperature increases, more electrons break free from covalent bonds, increasing the number of free electrons available for conduction
• Negative temperature coefficient: semiconductors have a negative temperature coefficient of resistance — meaning resistivity falls as temperature rises
• Opposite to metals: in metals, resistivity increases with temperature because lattice vibrations obstruct electron flow — semiconductors behave exactly the opposite
• Intrinsic semiconductors: silicon and germanium are classic examples — both show dramatic decrease in resistivity when heated
• Practical application: this property is exploited in thermistors — temperature-sensing devices that use the change in resistance to measure temperature accurately