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. In an intrinsic semiconductor, thermal excitation generates equal numbers of free electrons ( n_e ) and holes ( n_h ), so n_e = n_h = n_i , where n_i is the intrinsic carrier concentration. Substituting values gives Number of holes ( n_h ), which matches expected behaviour for this semiconductor device configuration, confirming doping, depletion and rectifier principles.