3. A material has an effectively full valence band and an empty conduction band. Explain why that if these two bands overlap the material behaves as a metal and if they are separated by a few electron volts in energy the material is an insulator.
4. Calculate the minimum energy a photon must have to produce an electron hole pair in an extrinsic semiconductor of band gap 1.0 electron volts.
Word file explains the effects of overlapping valence and conduction bands and calculates the minimum energy a photon must have for an electron hole pair in a semiconductor.