Electronic Devices and Circuits

Electrons and Holes in Semiconductor

Question 1
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 2
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.
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%
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 5
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 6
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 7
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 8
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 9
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 10
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,