# ELECTRONICS ENGINEERING – SEMICONDUCTOR MATERIALS MCQs

This section of Electronics engineering Multiple Choice Questions and Answers (MCQs) focuses on the “ Semiconductor materials ”. These MCQs are very helpful for the preparation of  University exams, Engineering exams, and various Technical competitive exams .

ELECTRONICS ENGINEERING – SEMICONDUCTOR MATERIALS MCQs

1. The conductivity of the semiconductor……….with the increase in temperature.

Explanation
:- The conductivity of semiconductors depends on the temperature. It increases with the increase of temperature because as temperature increases, the electron-hole pair is created. Due to more free charge carriers, current increase and conductivity increase.

2. silicon(Si) is most widely used material than germanium(Ge) because:

ANSWER= (C) Leakage current is more in germanium than in silicon.
Explanation:- The valence electrons of Ge are in the fourth shell while those in silicon are in the third shell. As Ge valence electrons are at a higher energy level, so need less energy to produce electron-hole pairs than the silicon. Hence leakage current is more in Ge than si. This property makes Ge more unstable at high temperatures. Therefore silicon is widely used material than germanium.

3. Which one of the following charge carriers exists in the forbidden energy gap of a semiconductor:

Explanation:- The forbidden energy gap is the energy gap that separates the valance band from the conduction band and normally no charge carrier exists in the forbidden energy gap.

4. The semiconductor material has a negative temperature coefficient of resistance.

Explanation:- The semiconductor material has a negative temperature coefficient of resistance because with the increase in temperature of semiconductor its resistance decreases and vice versa . Due to this property semiconductor behaves as a conductor at a very high temperature and as an insulator at a very low

5. Types Questions

Explanation:-When the temperature of an intrinsic semiconductor is increased then the covalent bond will break and an electron leaves the valance band and becomes free for conduction, so the empty space of electron in the valence band is known as a hole. Therefore electrons and holes are produced in pairs. Hence the concentration of electrons and holes are the same.

6. In a p-type semiconductor the minority charge carriers are:

Explanation:- In a P-type semiconductor the majority charge carriers are holes and minority charge carriers are electrons, while in N-type semiconductors the majority charge carriers are electrons and minority charge carriers are holes.

7. A semiconductor is always said to be electrically neutral because it has:

ANSWER= (D) an equal number of positive and negative charge carriers.
Explanation:- In a semiconductor if we add for example donor impurity to make an N-type semiconductor then the donor atom gives an extra electron to the semiconductor and then the donor atom itself will become a positive ion due to the release of an electron. So donor impurity has contributed an equal number of positive charges (donor becomes positive ion)and negative charges (free electrons)to the semiconductor. Hence the same number of positive and negative charge neutralizes each other and semiconductor always remains electrically neutral.

8. Which type of impurity is added in an intrinsic semiconductor to obtain an N-type semiconductor:

Explanation: When we add a pentavalent impurity atom in an intrinsic semiconductor, then out of 5 valance electrons of the pentavalent atom, 4 valence electrons form a covalent bond with 4 silicon atoms and the fifth valance electron of the pentavalent atom becomes free at room temperature. So one pentavalent impurity atom has donated one extra electron to the semiconductor and hence the number of electrons increases and the electron becomes the majority charge carrier so intrinsic semiconductor becomes N-Type semiconductor.

9. Which one of the following is an Acceptor type impurity:

Explanation:- Acceptor impurity has 3 valance electrons i.e Trivalent. Boron has 3 valance electron while Phosphorous, Arsenic, and Antimony has 5 valence electron. So Boron is an acceptor impurity.

10. Intrinsic semiconductors, at absolute zero temperature (0°k) behaves as: