Courses

## 10 Questions MCQ Test Electronic Devices | Test: Carrier Lifetime

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

### What is the range of the carrier lifetime?

Solution:

Carrier lifetime is defined as the existence of any carrier for τ seconds. Carrier lifetime ranges from nanoseconds to hundreds of microseconds.

QUESTION: 2

### What is the process number of Schokley-Read-Hall Theory processes?Process-‘ The capture of an electron from the conduction band by an initially neutral empty trap’

Solution:

This is the first process of Schokley-Read-Hall theory of Recombination.

QUESTION: 3

### Calculate the recombination rate if the excess carrier concentration is 1014cm-3 and the carrier lifetime is 1µseconds.

Solution:

The recombination rate, R=δn/τ.
So, R=1014 / 10-6
R=1020.

QUESTION: 4

Calculate the capture rate where Cn=10, Nt=1010cm-3, n=1020 and fF (Et)=0.4.

Solution:

Rcn=Cn*N_t*(1-fF (Et))*n
Substituting the values,
Rcn=6*1030.

QUESTION: 5

Calculate the emission rate where En=2.5, Nt=1010cm-3 and fF (Et)=0.6 .

Solution:

Ren=En*Nt*(fF (Et))
Substituting the values,
Ren=1.5*1010.

QUESTION: 6

At what condition, the rate of electron capture from the conduction band and the rate of the electron emission back into the conduction band must be equal?

Solution:

At thermal equilibrium, the electron capture rate and the emission rate will be same in the conduction band.

QUESTION: 7

Calculate the carrier lifetime when Cp=5 and Nt=1010cm-3.

Solution:

τp=1/(Cp*Nt )
=1/(5*1010)
=2*10-11.

QUESTION: 8

The number of majority carriers that are available for recombining with excess minority carriers decreases as the excess semiconductor becomes intrinsic. Is it true?

Solution:

With the increase in the number of the majority carriers, the carriers for the recombination will be decreasing with the excess minority carriers and will finally become intrinsic as the concentrations will be same.

QUESTION: 9

Which of the following is used as the recombination agent by semiconductor device manufactures?

Solution:

Gold is used as a recombination agent because of its chemical properties as it was used in the Bohr’s experiment. Thus the device designer can obtain the desired carrier lifetimes by introducing gold into silicon under controlled conditions.

QUESTION: 10

The rate of change of the excess density is proportional to the density. Is it true of false?

Solution:

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.