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. At 0 K, no thermal energy is available to excite electrons across the energy gap, so an intrinsic semiconductor has no free carriers and acts like an insulator. Substituting values gives Insulator, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.