Rankers Physics

Properties of Semiconductors: Practice Problem & Solution

C and Si both have same lattice structure, having 4 bonding electrons in each. However, C is insulator whereas Si is intrinsic semiconductor. This is because: (2012 Pre)
In case of C the valence band is not completely filled at absolute zero temperature.
In case of C the conduction band is partly filled even at absolute zero temperature.
The four bonding electrons in the case of C lie in the second orbit, whereas in the case of Si they lie in the third.
The four bonding electrons in the case of C lie in the third orbit, whereas for Si they lie in the fourth orbit.

Solution Explained:

To solve this problem, we apply the core principles of Properties of Semiconductors. Understanding the underlying formula is key to arriving at the correct answer below:

Carbon's valence electrons are in the second orbit, which is closer to the nucleus and more tightly bound than Silicon's valence electrons in the third orbit. This results in a much larger energy band gap for Carbon, making it an insulator.[cite: 1]

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