Extrinsic (n- and p-type) semiconductors
The semiconducting properties of Si and Ge can be enhanced
by doping these elements with atoms of a group 13 or group
15 element. Doping involves the introduction of only a
minutely small proportion of dopant atoms, less than 1 in
106, and extremely pure Si or Ge must first be produced.
The reduction of SiO2 in an electric furnace gives Si, and
the Czochralski process (see Box 5.3) is used to draw
single crystals of Si from the melt. We describe how dopants
are introduced into semiconductors in Section 27.6.