MCQ on Semiconductor Device

Electronic circuit components are built from a substance that is neither a good conductor nor an excellent insulator which is a semiconductor. Because of their compactness, dependability, and low cost, such gadgets have found widespread use. They’re used in power devices, optical sensors, and light emitters, including solid-state lasers, as discrete components.

With current values ranging from a few nano amperes (10-9 ampere) to more than 5,000 amperes and voltage ratings exceeding 100,000 volts, they can handle a wide variety of current and voltage. More importantly, semiconductor devices are well suited to be integrated into complicated but easily manufactured microelectronic circuits.

Q1. What is the resistivity of a semiconductor?

a) More than that of insulators and conductors

b) Between that of insulators and conductors

c) Less than that of insulators and conductors

d) None of the above

Answer- (b).Lies between that of insulators and conductors as because semiconductors are materials with electrical conductivities that fall in between that of good conductors and that of insulators.

Semiconductors have a resistivity ranging from 10-5 to 104  ohm-meter, whereas conductors have a resistivity ranging from 10-7 to 10-6 ohm-meter and insulators have a resistivity ranging from 107 to 108 ohm-meter.

Q.2. Which among the following is the most widely used semiconductor material?

a) Potassium

b) Phosphorous

c) Silicon

d) Arsenic

Answer. (c).Silicon as Si is the most extensively used semiconductor material because it has a wide temperature range and is plentiful, inexpensive, and simple to produce. Germanium was one of the first semiconductor materials to be invented, and while it is less extensively utilised than silicon, when alloyed with silicon, it can be used in very high-speed devices.

Q3. The energy gap between the valence band and the conduction band in a semiconductor is 

a) 5 eV

b) 10 eV

c) 15 eV

d) 1 eV

Answer. (d).1eV as because the energy band gap, also known as the energy gap, is the difference between the highest valence band and the lowest conduction band. Semiconductors have the same band structure as insulators, but with a significantly smaller energy gap, on the scale of 1 eV.

Q.4. What is the sign of the temperature coefficient of resistance in a semiconductor?

a) Negative

b) Positive

c) Zero

d) None of the above

Answer. (a).Negative as because Semiconductors are materials that have a nearly empty conduction band and a nearly filled valence band with a very tiny energy gap separating the two bands in terms of energy bands. As the temperature rises, more valence electrons cross across to the conduction band, resulting in an increase in conductivity. This demonstrates that a semiconductor’s electrical conductivity increases as temperature rises, implying that a semiconductor has a negative temperature coefficient of resistance.

Q.5. How many valence electrons are there in semiconductors?

a) 2

b) 3

c) 4

d) 6

Answer. (c).4 as because silicon, germanium, and gallium arsenide are the most prevalent semiconductor elements. The most extensively used semiconductor material is silicon. Its orbits contain 14 protons and 14 electrons. The valence bond of an individual silicon atom has four electrons. Germanium, like silicon, contains 32 protons, 32 electrons, and 4 valence electrons.

Ques.6. What is the resistivity of pure germanium under the standard condition?

a) 6 × 104Ω cm

b) 60 Ω cm

c) 3 × 10-3Ω cm

d) 6 × 10-4Ω cm

Answer. (b) 60 Ω cm.

Q.7. The resistivity of pure silicon is 

a) 100 Ω cm

b) 60,000 Ω cm

c) 3 × 106Ω cm

d) 6 × 10-8Ω cm

Answer. (a).100 Ω cm.

Q.8. When a pure semiconductor is heated, what will be the effect on its resistance?

a) Goes down

b) Goes up

c) Remains the same

d) None of the above

Answer. (a).Goes down.

Q.9. Where does the strength of a semiconductor crystal come from?

a) Forces between nuclei

b) Force between protons

c) Electrons-Pairs bonds

d) None of the above

Answer. (c)Electrons-Pairs bonds.

Q.10. When a pentavalent impurity is introduced into a pure semiconductor, it transforms into

a) Intrinsic

b) n-type

c) p-type

d) None of the above

Answer. (b).n-type.

Q.11. What does the addition of pentavalent impurity to semiconductors create?

a) Free Electrons

b) Holes

c) Valence electrons

d) Bound electrons

Answer. (a).Free Electrons.

Q.12. How many valence electrons are there in a pentavalent impurity?

a) 3 Valence electrons

b) 6 Valence electrons

c) 4 Valence electrons

d) 5 Valence electrons

Answer. (d).5 Valence electrons as because the n-type semiconductors with a pentavalent (phosphorus) impurity, where “n” stands for negative, conduct because surplus electrons are transferred. A donor is a pentavalent atom, meaning it possesses five valence electrons. In a silicon crystal, each donor produces one free electron. Because the free electrons outweigh the holes in an n-type semiconductor, the free electrons are the majority carriers, while the holes are the minority carriers.

Q.13. What is the charge on a n-type semiconductor?

a) Positively charged

b) Electrically neutral

c) Negatively charged

d) None of the above

Answer. (b).Electrically neutral.

Q.14. How many valence electrons are there in a trivalent impurity?

a) 3 Valence electrons

b) 5 valence electrons

c) 6 valence electrons

d) 4 valence electrons

Answer. (a).3 Valence electrons.

Q.15. What is the other name for a pentavalent impurity?

a) Donor impurity

b) Acceptor impurity

c) Ionic impurity

d) None of the above

Answer. (a).Donor impurity because Pentavalent impurities are elements with five valence electrons in their atoms, such as As, P, Sb, and others. Because they provide an extra free electron, these impurities are also known as donor impurities.

Q.16. What is the effect on the bulk resistance on a semiconductor by adding impurities?   

a) Decreases

b) Remain the same

c) Increases

d) None of the above

Answer. (a).Decreases.

Q.17. What will happen when a hole and electron are in close proximity?

a) Repel each other

b) Have no effect on each other

c) Attract each other

d) None of the above

Answer. (c).Attract each other as because in a neutral medium, an electron stimulated into the conduction band is a negatively charged particle that interacts with the hole formed in the valence band (positively charged particle). This pair of charged particles is formed locally, and the Coulomb force attracts them together.