Question

C, Si and Ge have same lattice structure. Why is C insulator, while Si and Ge intrinsic semiconductors ?

Answer 1

The intrinsic and insulator property depends upon the free electrons and band gap property.

• As the C that is carbon is insulator, which is due to the free electrons because the carbon never lose or gain electrons which made the property of insulator.
• The Si and Ge that are silicon and germanium, these do not have free electron but they are used for doping that is why the property of intrinsic came there.
• As we start moving from the carbon to germanium there intrinsic property goes on increasing.
• They have same structure but difference came in the property of reacting with the other elements with different methods.

Answer 2

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• The 4 bonding electrons of C, si or Ge lie, respectively , in the second , third and fourth orbit.
• Hence, energy required to take out an electron from these atoms will be least for Ge, followed by Si and highest fir C.
• Hence, number of free electrons conduction in Ge and Si are significant but negligibly small for C.