Question

Electric conduction in a semiconductor takes place due to
A. electrons only
B. holes only
C. both electrons and holes
D. neither electrons or holes

Answer 1

Hint: Semiconductors are the material which have the conductivity in between the conductors (mostly metals) and the insulators like ceramics. Semiconductors may be pure elements like silicon or the compounds like gallium arsenide. To change the conductivity of the semiconductor material doping is done.

Complete answer:
In the simple metals like copper the electricity conduction takes place due to the electrons but in the semiconductors the conduction of the electricity takes place due to electrons and the absence of the electrons also. Absence of the electrons is known as holes.

Holes are formed when the electrons from the outermost shell of the atom that is completely filled with the electrons move out to the conduction band. Conduction bands are the area where electrons can easily escape.

By performing the doping, we get the two types of the semiconductors: p-type semiconductors and the n-type semiconductors.

n-type semiconductors- when pentavalent elements like arsenic and phosphorus are added to the tetravalent pure semiconductor elements like silicon then it provides an extra free electron. Since electrons are negatively charged, the obtained material after doping is called a n-type semiconductor.
p-type semiconductors- when the trivalent elements like boron and gallium are doped with the pure semiconductors then there will be absence of an electron in the semiconductor crystal. Like this the holes are created which are assumed to be positively charged and the resultant material is called as p-type semiconductors.

Hence in the semiconductors electric conduction takes place due to electrons and holes both.

So, the correct answer is “Option C”.

Note:
In p-type semiconductor the holes are majority carriers whereas the electrons are the minority carriers while in the n-type semiconductors the electrons are majority carriers and the holes are minority carriers. To get the n-type of the semiconductors we have to dope the pure semiconductors like silicon with the pentavalent metals which give rise to the electrons as majority carriers.