Question

The energy gap in a semiconductor
(A) Increase with temperature
(B) Does not change with temperature
(C) Decrease with temperature
(D) Is zero

Answer 1

Hint:Semiconductor are a class of naturally occurring elements and they have the conductivity level in between those of conductors and non-conductors. Under conditions of temperature they behave as conductors and non-conductors. The elements in group 14, 15 and 16 usually fall in the category of semiconductors and some notable examples are silicon, phosphorus, arsenic etc.

Complete answer:
The energy gap refers to the gap between the conduction band and the valence band. At the atomic level when we talk about the ability of the material to conduct electricity, the free electrons play a very important role. Initially for the semiconductors all the electrons are in the valence band and the conduction band is empty. The difference of energy level between these two bands is a function of temperature. With the increase in temperature, the energy gap decreases.

So, the correct option is C.

Note: Doping is done in a semiconductor to increase the conductivity of the semiconductor. The semiconductor of group 14 has 4 electrons in their outermost shell and they need 4 electrons to complete the octet. The elements of group 13 have 3 electrons in their shell when group 13 is doped, then there is vacancy of one electron which results in hole and the hole is the majority charge carrier. There are called p type semiconductors. While on the other hand when group 15 element is doped then there is an excess of one electron and these types are called n types of semiconductor.