Practice question

**Semiconductor properties** distinguish from conductors and insulators by temperature dependence and doping response. At 0 K intrinsic acts as insulator, conductivity due to thermally generated electron-hole pairs, number of outer electrons 4 for Si/Ge forming covalent bonds, each atom shares electrons, crystal with N atoms has 4N valence electrons, 2N bonds. Pentavalent donor impurities (e.g., As, P) in an n-type semiconductor donate extra electrons for conduction, significantly increasing the number of free electrons beyond intrinsic levels. Substituting values gives Extra electrons, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.