Silicon atom plays important role in the manufacturing of the semiconductor device. So you can say that silicon is a heart of every electronic device. Silicon atom is widely used than the germanium. Silicon atom has 4 valence electron in the outer most orbit. It was realized that silicon atom was superior to the germanium atom.
As shown in the above figure silicon atom have 4 valence electron in 3rd orbit. Germanium has 4 valence electron in 4th orbit. This makes a big difference. The germanium valence electrons are at a higher energy level as valence electrons are away from the nucleus. For this reason, the germanium atom is more unstable at a higher temperature. Due to this reason silicon atom is superior to the germanium atom.
Now let’s see the energy band diagram of the silicon atom.
The figure shows the energy band diagram of the silicon atom. Silicon atom has 14 electrons as silicon atomic number is 14. All 14 electrons are distributed in 3 orbits. All energy level is associated with a certain amount of energy. And all bands are separated from the adjacent bands by the energy gap.No electron can exist in the energy gap.
For an electron to jump from one orbit to the other orbit require external energy. And external energy is equal to the energy difference between the two energy level. The valence band has an energy level of 0.7 eV. The conduction band is shown to have 1.8 eV. Thus for an electron to jump from the valence band to conduction band 1.8-0.7=1.1eV, energy must be supplied.