1. A semiconductor is a substance which has resistivity (10^-4 to 0.5Ωm) in between conductors and insulators e.g. germanium, silicon, selenium, carbon e.t.c
2. It is a substance which has almost filled valence band and nearly empty conduction band with a very small energy gap (= 1 eV) separating the two.
3. A semiconductor material is one whose electrical properties lie in between those of insulators and good conductors e.g. germanium and silicon
4. A material having volume resistivity less than that of insulators but much greater than that of such good conductors as metals.
