SOLUTION

• Pure semiconductors are known as intrinsic semiconductors. Frequently available semiconductors are germanium and silicon Isis belonging to the IV group in the periodic table.
• Each semiconductor has four valence electrons in its outermost orbit.
• To set stability, each of these atoms makes four covalent bonds with the surrounding four neighboring atoms in the semiconductor crystal.
• The two-dimensional representation of silicon intrinsic semiconductor at 0 K along with the energy band structure is as shown in Fig.

At 0K, all valence electrons are strongly bound to their atoms and are actively participating in the covalent bond formation. As a result, no free electrons are available for conduction and it acts as an insulator.