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. The charge of additional carriers (electrons in n-type or holes in p-type) is balanced by the equal and opposite charge of ionized dopant cores (positive in n-type, negative in p-type). Substituting values gives Charge of carriers equals that of ionized cores, which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.