Germanium semiconductor atom has ‘atomic number’ Z = 32. It has 32 positive charges in the nucleus and 32 electrons in various shells containing 2, 8, 18 and 4 electrons. Germanium atom is electrically neutral. Germanium semiconductor as a whole is electrically neutral.
- First, second and third orbits are completely filled.
- Fourth orbit (shell) is partially filled.
- Energy levels from fifth orbit onwards are empty energy levels.
Germanium atom representation is shown in Fig. 2.4. It is a basis to know the formation of covalent bonds and so on. Germanium is also considered as a ‘tetravalent’ material, as it has 4 valence electrons in its outer incomplete shell. Thus, Silicon and Germanium materials are referred as tetravalent materials with similar electrical and chemical properties.
Fig. 2.4 Representation of germanium atom with four valence electrons