Fig 3.1a The germanium atom
The germanium atom has a total of 32 electrons in four rings which from the centre outwards contain two, eight, 18 and four electrons. The four electrons in the outer ring, as in the case of the silicon atom, join with those of adjacent atoms to form a crystal lattice. Because the outer electrons are one ring further away from the nucleus, they can become detached more easily than in the silicon atom. Semiconductors made using germanium are nowadays normally used where signal levels are low. They are generally less robust than their silicon counterparts, ie their power handling capabilities are lower, and they are more easily damaged by static discharge (ESD).
