Practice question

**Types of semiconductors** elemental Si, Ge group IV with 4 valence electrons, compound GaAs, InP etc. Intrinsic has n_e = n_h, extrinsic doped with pentavalent donors (P, As) gives n-type excess electrons, trivalent acceptors (B, Al) gives p-type excess holes, resistivity range semiconductors 10⁻⁵ to 10⁶ Ω·m vs insulators 10¹¹ Ω·m. Semiconductors have intermediate conductivity ( 10⁵ to 10⁻⁶ S m⁻¹ ), between metals ( 10² to 10⁸ S m⁻¹ ) and insulators ( 10⁻¹¹ to 10⁻¹⁹ S m⁻¹ ). Substituting values gives Intermediate to metals and insulators, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.