At room temperature of 300°K, it requires an energy of EG = 1.12 eV to break covalent bonds in Silicon material and EG = 0.7 eV to break the covalent bonds in Germanium material and to produce some ‘electron–Hole pairs’.
Even at room temperature, a few of the covalent bonds will be broken, leading to equal number of electrons and Holes in Conduction Band and Valence Band, respectively. Electrons in the Conduction Band and Holes in the Valence Band, in an intrinsic semiconductor, are shown in Fig. 2.12. Small dashes represent free or conduction electrons. Holes are represented by circles in valence band.
Fig. 2.12 Energy-band diagram for an intrinsic semiconductor