Electronic Devices and Circuits

Electrons and Holes in Semiconductor

Question 1
Marks : +2 | -2
Pass Ratio : 100%
The thermal equilibrium concentration of the electrons in the conduction band and the holes in the valence band depends upon?
Effective density of states
Fermi energy level
Both A and B
Neither A nor B
Explanation:
The electrons and holes depends upon the effective density of the states and the Fermi energy level given by the formula,
Question 2
Marks : +2 | -2
Pass Ratio : 100%
In a semiconductor which of the following carries can contribute to the current?
Electrons
Holes
Both
None
Explanation:
In a semiconductor, two types of charges are there by which the flow of the current takes place. So, both the holes and electrons take part in the flow of the current.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
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
n(E)=gc(E)*fF(E)
n(E)=gc(-E)*fF(E)
n(E)=gc(E)*fF(-E)
n(E)= gc(-E)*fF(-E)
Explanation:
The distribution of the electrons in the conduction band is given by the product of the density into Fermi-dirac distribution.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The intrinsic Fermi level of a semiconductor depends on which of the following things?
Emidgap
mp*
mn*
All of the mentioned
Explanation:
Question 5
Marks : +2 | -2
Pass Ratio : 100%
In which of the following semiconductor, the concentration of the holes and electrons is equal?
Intrinsic
Extrinsic
Compound
Elemental
Explanation:
In the intrinsic semiconductor, ni=pi that is the number of the electrons is equal to the number of the holes. Whereas in the extrinsic conductor ni is not equal to pi.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
What is the intrinsic electrons concentration at T=300K in Silicon?
1.5*1010cm-3
1.5*10-10cm-3
2.5*1019cm-3
2.5*10-19cm-3
Explanation:
Using the formula,
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Which of the following expressions represent the Fermi probability function?
fF(E)=exp(-[E-EF]/KT)
fF(E)=exp(-[EF-E]/KT)
fF(E)=exp([E-EF]/KT)
fF(E)=exp(-[EF-E]/KT)
Explanation:
It is the correct formula for the Fermi probability function.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
What is the value of the effective density of states function in the conduction band at 300k?
3*1019 cm-3
0.4*10-19 cm-3
2.5*1019 cm-3
2.5*10-19 cm-3
Explanation:
Question 9
Marks : +2 | -2
Pass Ratio : 100%
What is the difference between the practical value and theoretical value of ni?
Factor of 1
Factor of 2
Factor of 3
Factor of 4
Explanation:
This is practically proved.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
Electrons from valence band rises to conduction band when the temperature is greater than 0 k. Is it True or False?
True
False
Explanation:
As the temperature rises above 0 k, the electrons gain energy and rises to the conduction band from the valence band.