Explore topic-wise InterviewSolutions in .

This section includes InterviewSolutions, each offering curated multiple-choice questions to sharpen your knowledge and support exam preparation. Choose a topic below to get started.

51.

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 BI had been asked this question by my school teacher while I was bunking the class.Asked question is from Electrons and Holes in Semiconductor topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right choice is (c) Both A and B

To EXPLAIN: The electrons and holes depends upon the EFFECTIVE density of the STATES and the Fermi energy level GIVEN by the formula,

.
Discussion
52.

The current entering the volume at x is I and leaving is I+Δi , the number of coulombs per second will be equal to δI. Is it true or false?(a) True(b) FalseThis question was addressed to me by my school teacher while I was bunking the class.My doubt is from The Continuity Equation in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right choice is (a) True

To explain I would say: Coulombs PER second is known as the current. The DIFFERENTIAL current will be the current through the SEMICONDUCTOR.
Discussion
53.

Which of the following represents the best definition for the diffusion length for holes?(a) Average distance which an electron is injected travels before recombining with an electron(b) Average distance which a hole is injected travels before recombining with an electron(c) Average distance which a hole is injected travels before recombining with a hole(d) Average distance which an electron is injected before recombining with a holeI have been asked this question during a job interview.My doubt stems from The Continuity Equation in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»
Discussion
54.

What is the diffusion length for holes when Dp=25cm^2/s and τp=25s?(a) 25cm(b) 1cm(c) 0.04cm(d) 50cmI have been asked this question in an interview for internship.The question is from The Continuity Equation topic in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right choice is (a) 25cm

The best EXPLANATION: Lp=√(Dp*τp)

=√(25*25)

=25cm.
Discussion
55.

Consider a silicon wafer having Nc=2.8*10^19cm^-3 and the Fermi energy is .25eV below the conduction band. Calculate the equilibrium concentrations of electrons at T=300K?(a) 18*10^16cm^-3(b) 1.8*10^16cm^-3(c) 1.8*10^14cm^-3(d) 180*10^16cm^-3The question was asked during an interview for a job.My question is based upon Charge Densities in a Semiconductor impurities topic in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT ANSWER is (a) 18*10^16cm^-3

Best EXPLANATION: n0=Nc*EXP(-Eg/KT)=2.8*10^19*exp(-0.25/0.0259)

=18*10^16cm^-3.
Discussion
56.

For which type of material, the number of free electron concentration is equal to the number of donor atoms?(a) P type semiconductor(b) Metal(c) N-type semiconductor(d) InsulatorThis question was addressed to me in a job interview.My question is from Charge Densities in a Semiconductor impurities in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer»
Discussion
57.

At absolute zero temperature, which level is above the Fermi energy level in the case of donors?(a) Donor energy level(b) Acceptor energy level(c) Conduction Band(d) Valence BandI had been asked this question in homework.The question is from Donor and Acceptor impurities topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct ANSWER is (c) CONDUCTION Band

Best explanation: At T=0 K, the tem exp(-∞)=0 in the EXPRESSION of

Thus, EF>ED

So, only conduction band lies above the Fermi energy LEVEL.
Discussion
58.

In the Hall Effect, the directions of electric field and magnetic field are parallel to each other.(a) The above statement is(b) True(c) FalseI had been asked this question in my homework.This interesting question is from The Hall Effect in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct choice is (B) True

The best I can EXPLAIN: To MAKE Lorentz force into the EFFECT, the electric field and MAGNETIC field should be perpendicular to each other.
Discussion
59.

Calculate the carrier lifetime when Cp=5 and Nt=10^10cm^-3.(a) 2*10^11(b) 2*10^-11(c) 20*10^-11(d) 20*10^11The question was posed to me in an online interview.Question is from Carrier Life time in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right choice is (B) 2*10^-11

To explain I WOULD say: τp=1/(Cp*NT )

=1/(5*10^10)

=2*10^-11.
Discussion
60.

What is the direction of the electron diffusion current density relative to the electron flux?(a) Same direction(b) Opposite to each other(c) Perpendicular to each other(d) At 270 degrees to each otherThis question was posed to me in a job interview.I'd like to ask this question from Diffusion topic in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT option is (b) Opposite to each other

The explanation: From the GRAPH between ELECTRON concentration and the DISTANCE, we can SEE that the direction of the electron diffusion current density is opposite to the electron flux.
Discussion
61.

What is the SI unit of electron diffusion constant?(a) cm^2/s(b) m^2/s(c) m/s(d) noneThe question was asked in homework.My enquiry is from Diffusion topic in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT answer is (b) m^2/s

The BEST I can explain: J=eDdn/dx

So D=Q*m/ (q*s*(1/m))

=m^2/s.
Discussion
62.

Which of the following expression represent the correct formulae for calculating the exact position of the Fermi level for p-type material?(a) EF = EV + kTln(ND / NA )(b) EF = -EV + kTln(ND / NA )(c) EF = EV – kTln(ND / NA )(d) EF = -EV – kTln(ND / NA )The question was posed to me in an interview.I want to ask this question from Fermi Level in a Semiconductor having Impurities topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right OPTION is (a) EF = EV + kTln(ND / NA )

BEST explanation: The correct POSITION of the Fermi level is found with the formula in the ‘a’ option.
Discussion
63.

Do the intrinsic Fermi energy level changes with the addition of dopants and acceptors?(a) True(b) FalseI had been asked this question in final exam.My doubt is from Charge Densities in a Semiconductor impurities topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct choice is (b) False

Best explanation: 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.
Discussion
64.

Which of the following band is just above the intrinsic Fermi level for n-type semiconductor?(a) Donor band(b) Valence band(c) Acceptor band(d) Conduction bandThis question was addressed to me in an online interview.The above asked question is from Donor and Acceptor impurities topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT option is (a) Donor BAND

The EXPLANATION: For n-type SEMICONDUCTORS, the donor band is just above the intrinsic Fermi level.
Discussion
65.

Calculate the hall voltage when the Electric Field is 5V/m and height of the semiconductor is 2cm.(a) 10V(b) 1V(c) 0.1V(d) 0.01VI got this question in a national level competition.This interesting question is from The Hall Effect in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT CHOICE is (C) 0.1V

The BEST I can EXPLAIN: Vh=E*d

=5*2/100

=0.1V.
Discussion
66.

Consider a bar of silicon having carrier concentration n0=10^15 cm^-3 and ni=10^10cm^-3. Assume the excess carrier concentrations to be n=10^13cm^-3, calculate the quasi-fermi energy level at T=300K?(a) 0.2982 eV(b) 0.2984 eV(c) 0.5971 eV(d) 1EvThe question was posed to me in an interview.The above asked question is from Fermi Level in a Semiconductor having Impurities topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct CHOICE is (B) 0.2984 eV

Explanation: =1.38*10^-23*300*LN(10^13+10^15/10^13)

=0.2984 eV.
Discussion
67.

Which of the following term isn’t a part of the total current density in a semiconductor?(a) Temperature(b) µ(c) e(d) EThis question was posed to me during an interview for a job.My doubt is from Diffusion in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The correct choice is (a) TEMPERATURE

To ELABORATE: J=enµE+epµE+eDdn/dx-eDdp/dx

So, temperature isn’t a PART of the equation.
Discussion
68.

Which states get filled in the conduction band when the donor-type impurity is added to a crystal?(a) Na(b) Nd(c) N(d) PThe question was posed to me in an interview.The query is from Fermi Level in a Semiconductor having Impurities topic in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right answer is (B) Nd

The explanation is: When the donor-type impurity is added to a CRYSTAL, FIRST Nd STATES get FILLED because it is of the highest energy.
Discussion
69.

If Ef>Efi, then what is the type of the semiconductor?(a) n-type(b) P-type(c) Elemental(d) CompoundI had been asked this question in my homework.This question is from Charge Densities in a Semiconductor impurities topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct OPTION is (a) n-type

Easy explanation: 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.
Discussion
70.

In which of the following semiconductor, the concentration of the holes and electrons is equal?(a) Intrinsic(b) Extrinsic(c) Compound(d) ElementalI got this question during a job interview.The question is from Electrons and Holes in Semiconductor topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The correct answer is (a) Intrinsic

Easiest 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.
Discussion
71.

Is n/p=ni^2 is a correct formula?(a) True(b) FalseThis question was posed to me in an international level competition.The above asked question is from Charge Densities in a Semiconductor impurities topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT OPTION is (B) False

Explanation: The correct FORMULA is N*p=ni^2.
Discussion
72.

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 4This question was addressed to me by my school teacher while I was bunking the class.The question is from Electrons and Holes in Semiconductor topic in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right CHOICE is (B) FACTOR of 2

The explanation: This is PRACTICALLY proved.
Discussion
73.

Which of the following parameters can’t be found with Hall Effect?(a) Polarity(b) Conductivity(c) Carrier concentration(d) Area of the deviceThis question was posed to me in unit test.I want to ask this question from The Hall Effect in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right CHOICE is (d) Area of the device

To explain I WOULD say: The Hall Effect is used for FINDING the whether the semiconductor is of n-type or p-type, mobility, CONDUCTIVITY and the carrier concentration.
Discussion
74.

The rate of change of the excess density is proportional to the density. Is it true of false?(a) True(b) FalseThis question was addressed to me in class test.This question is from Carrier Life time in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT OPTION is (a) True

The explanation: The rate of change of the excess DENSITY depends on the density of the semiconductor and the rate with respect to time is also DEPENDENT on it.
Discussion
75.

Calculate the capture rate where Cn=10, Nt=10^10cm^-3, n=10^20 and fF (Et)=0.4.(a) 6*10^30(b) 5*10^30(c) 36*10^30(d) 1.66*10^29This question was posed to me during a job interview.I want to ask this question from Carrier Life time topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT ANSWER is (a) 6*10^30

To EXPLAIN I WOULD say: Rcn=Cn*N_t*(1-fF (Et))*n

Substituting the values,

Rcn=6*10^30.
Discussion
76.

Which of the following parameter describes the best movement of the electrons inside a semiconductor?(a) Velocity gradient(b) Diffusion(c) Mobility(d) Density gradientI have been asked this question in homework.My doubt stems from Diffusion topic in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT answer is (C) Mobility

To ELABORATE: Mobility is defined as the MOVEMENT of the electrons inside a semiconductor. On the other hand, VELOCITY gradient is the ratio of velocity to distance.
Discussion
77.

ThefF (E) decreases in which of the following band for p-type semiconductor?(a) Conduction band(b) Donor band(c) Acceptor band(d) Valence bandThis question was posed to me in an interview.This intriguing question originated from Charge Densities in a Semiconductor impurities topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT choice is (a) Conduction BAND

Easiest explanation: 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.
Discussion
78.

What do you mean by the tem ‘FREEZE-OUT’?(a) All the electrons are frozen at room temperature(b) None of the electrons are thermally elevated to the conduction band(c) All the electrons are in the conduction band(d) All the holes are in the valence bandI had been asked this question in an internship interview.Question is from Donor and Acceptor impurities in division Conduction in Semiconductors of Electronic Devices & Circuits

Answer» RIGHT option is (B) NONE of the ELECTRONS are thermally elevated to the conduction band

To explain: Freeze out means none of the electrons are TRANSMITTED to the conduction band.
Discussion
79.

What is the intrinsic electrons concentration at T=300K in Silicon?(a) 1.5*10^10cm^-3(b) 1.5*10^-10cm^-3(c) 2.5*10^19cm^-3(d) 2.5*10^-19cm^-3I had been asked this question in unit test.This question is from Electrons and Holes in Semiconductor topic in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT ANSWER is (a) 1.5*10^10cm^-3

The BEST explanation: Using the FORMULA,

We get, ni=1.5*10^10cm^-3.
Discussion
80.

In Hall Effect, the electric field applied is perpendicular to both current and magnetic field?(a) True(b) FalseI had been asked this question by my college director while I was bunking the class.My question is based upon The Hall Effect topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Right choice is (a) True

The explanation: In Hall Effect, the electric FIELD is PERPENDICULAR to both current and magnetic field so that the force DUE to magnetic field can be BALANCED by the electric field or vice versa.
Discussion
81.

In diffusion, the particles flow from a region of _______to region of ___________(a) High, low(b) Low , high(c) High , medium(d) Low, mediumI had been asked this question in homework.My doubt stems from Diffusion in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer» RIGHT ANSWER is (a) High, LOW

The best explanation: Diffusion is the process of flow of particles form the REGION of the high CONCENTRATION to a region of low concentration.
Discussion
82.

Calculate the Hall Effect coefficient when number of electrons in a semiconductor is 10^20.(a) 0.625(b) 0.0625(c) 6.25(d) 62.5This question was addressed to me by my school teacher while I was bunking the class.I'd like to ask this question from The Hall Effect in portion Conduction in Semiconductors of Electronic Devices & Circuits

Answer» CORRECT CHOICE is (B) 0.0625

Explanation: R=1/ρ

=1/(1.6*10^-19*10^20)

=0.0625.
Discussion
83.

Electrons from valence band rises to conduction band when the temperature is greater than 0 k. Is it True or False?(a) True(b) FalseThis question was posed to me during an interview.I'd like to ask this question from Electrons and Holes in Semiconductor topic in chapter Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

The CORRECT answer is (a) True

The best explanation: As the temperature rises above 0 K, the electrons gain ENERGY and rises to the conduction BAND from the valence band.
Discussion
84.

In a semiconductor which of the following carries can contribute to the current?(a) Electrons(b) Holes(c) Both(d) NoneI had been asked this question in homework.Query is from Electrons and Holes in Semiconductor topic in section Conduction in Semiconductors of Electronic Devices & Circuits

Answer»

Correct choice is (c) Both

The explanation is: 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.
Discussion