SOLUTION

• A perfect semiconductor with no impurities or lattice defects is called an intrinsic semiconductor.
• The generation of a hole in an intrinsic semiconductor is accomplished by breaking a covalent bond of the crystal producing a free electron and a vacancy in the lattice.
• Since free electrons and holes are created in pairs, the number of free electrons in the conduction band is always equal to the number of holes in the valence band i.e the ratio of the electron-hole pair is equal to 1.