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# Test: Charge Densities In A Semiconductor Impurities

## 10 Questions MCQ Test Electronic Devices | Test: Charge Densities In A Semiconductor Impurities

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This mock test of Test: Charge Densities In A Semiconductor Impurities for Electrical Engineering (EE) helps you for every Electrical Engineering (EE) entrance exam. This contains 10 Multiple Choice Questions for Electrical Engineering (EE) Test: Charge Densities In A Semiconductor Impurities (mcq) to study with solutions a complete question bank. The solved questions answers in this Test: Charge Densities In A Semiconductor Impurities quiz give you a good mix of easy questions and tough questions. Electrical Engineering (EE) students definitely take this Test: Charge Densities In A Semiconductor Impurities exercise for a better result in the exam. You can find other Test: Charge Densities In A Semiconductor Impurities extra questions, long questions & short questions for Electrical Engineering (EE) on EduRev as well by searching above.
QUESTION: 1

### Is n/p=ni2 is a correct formula?

Solution:

The correct formula is n*p=ni2.

QUESTION: 2

### Calculate the number of electrons is the number of holes are 15*1010?

Solution:

n*p=(1.5*1010)2
n*15*1010=1.5*1.5*1010*1010
n=1.5*109 electrons.

QUESTION: 3

### For which type of material, the number of free electron concentration is equal to the number of donor atoms?

Solution:

The n-type semiconductor has equal concentration of free electron and donor atoms.

QUESTION: 4

Identify the correct condition for a semiconductor to be electrically neutral.

Solution:

The sum of the number of donors and the holes is equal to the sum of the number of the acceptors and the electrons.

QUESTION: 5

Do the Fermi energy level changes in a semiconductor?

Solution:

The Fermi energy level changes as the electron and hole concentrations change because of the formula which defines the position of the Fermi level depending on the concentration of holes and electrons.

QUESTION: 6

Consider a silicon wafer having Nc=2.8*1019cm-3 and the Fermi energy is .25eV below the conduction band. Calculate the equilibrium concentrations of electrons at T=300K?

Solution:

n0=Nc*exp(-Eg/KT)=2.8*1019*exp(-0.25/0.0259)
=18*1016cm-3.

QUESTION: 7

If Ef>Efi, then what is the type of the semiconductor?

Solution:

For n-type, the Fermi energy level is greater than the intrinsic Fermi energy level because in an energy band, Fermi level of donors is always greater than that of the acceptors.

QUESTION: 8

The 1-fF (E) increases in which of the following band for n type semiconductor?

Solution:

For an n-type semiconductor, the probability of fF (E) decreases in the valence band. The probability of finding the electron in the conduction band is more.

QUESTION: 9

The fF (E) decreases in which of the following band for p-type semiconductor?

Solution:

The probability of finding the electron in the conduction band decreases for a p-type semiconductor because in a p-type semiconductor, the holes will be in conduction band rather than the electrons.

QUESTION: 10

Do the intrinsic Fermi energy level changes with the addition of dopants and acceptors?

Solution:

The intrinsic Fermi energy level always remains constant because it is an imaginary level taken to distinguish between the Fermi level of the types of semiconductor.