Electronic Devices and Circuits Questions and Answers – Electrons and Holes in Semiconductor

This set of Electronic Devices and Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Electrons and Holes in Semiconductor”.

1. Which of the following expressions represents the correct distribution of the electrons in the conduction band? (gc(E)=density of quantum states, fF(E)=Fermi dirac probability
a) n(E)=gc(E)*fF(E)
b) n(E)=gc(-E)*fF(E)
c) n(E)=gc(E)*fF(-E)
d) n(E)= gc(-E)*fF(-E)
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2. What is the value of the effective density of states function in the conduction band at 300k?
a) 3*10¹⁹ cm^-3
b) 0.4*10^-19 cm^-3
c) 2.5*10¹⁹ cm^-3
d) 2.5*10^-19 cm^-3
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Answer: c
Explanation:
Substituting the values of m_n=m0 ,h=6.626*10^-34J/s ,k=1.38*10^-23 and T=300K, we get
Nc=2.5*10¹⁹ cm^-3.

3. In a semiconductor which of the following carries can contribute to the current?
a) Electrons
b) Holes
c) Both
d) None
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4. Which of the following expressions represent the Fermi probability function?
a) fF(E)=exp(-[E-EF]/KT)
b) fF(E)=exp(-[EF-E]/KT)
c) fF(E)=exp([E-EF]/KT)
d) fF(E)=exp(-[EF-E]/KT)
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5. Electrons from valence band rises to conduction band when the temperature is greater than 0 k. Is it True or False?
a) True
b) False
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6. What is the intrinsic electrons concentration at T=300K in Silicon?
a) 1.5*10¹⁰cm^-3
b) 1.5*10^-10cm^-3
c) 2.5*10¹⁹cm^-3
d) 2.5*10^-19cm^-3
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Answer: a
Explanation: Using the formula,

We get, ni=1.5*10¹⁰cm^-3.

7. The intrinsic Fermi level of a semiconductor depends on which of the following things?
a) E_midgap
b) m_p^*
c) m_n^*
d) All of the mentioned
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Answer: d
Explanation:
From the above formula, E_fidepends on all of the options given.

8. What is the difference between the practical value and theoretical value of ni?
a) Factor of 1
b) Factor of 2
c) Factor of 3
d) Factor of 4
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9. The thermal equilibrium concentration of the electrons in the conduction band and the holes in the valence band depends upon?
a) Effective density of states
b) Fermi energy level
c) Both A and B
d) Neither A nor B
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Answer: c
Explanation: The electrons and holes depends upon the effective density of the states and the Fermi energy level given by the formula,
.

10. In which of the following semiconductor, the concentration of the holes and electrons is equal?
a) Intrinsic
b) Extrinsic
c) Compound
d) Elemental
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Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.