As the temperature of a semiconductor rises, its electrical conductivity:
Astays constant, being fixed by doping
Bdecreases, as the lattice vibrates more
Cincreases, as more carriers are freed
Dfalls to zero above room temperature
Answer & Solution
Correct answer: C. increases, as more carriers are freed
1. In a semiconductor most charge carriers are bound in covalent bonds at low temperature.
2. Heating supplies energy that breaks some of those bonds.
3. Each broken bond releases an electron and leaves a hole, so both carrier types increase.
4. More carriers means higher conductivity, so resistance falls as temperature rises.
5. This is the opposite of a metal, where extra lattice vibration scatters the already-free electrons and conductivity falls.
_Source: NECTA ACSEE 2023 Physics 131/1, Question 9: Electronics (Semiconductors,Logic Gates & Op-Amps)_