Testbook Logo
Exams SuperCoaching Test Series Skill Academy
More

Question

Download Solution PDF

The diffusion length for holes LP, is the 

This question was previously asked in
ESE Electronics 2010 Paper 1: Official Paper
Attempt Online
View all UPSC IES Papers >
  1. Average distance which an injected hole travels before recombining with an electron
  2. Maximum distance travelled by a hole before recombining with an electron
  3. Length of the region in which diffusion takes place
  4. Minimum distance travelled by a hole before recombines with an electron

Answer (Detailed Solution Below)

Option 1 : Average distance which an injected hole travels before recombining with an electron
Free Tests
View all Free tests >
Free
ST 1: UPSC ESE (IES) Civil - Building Materials
6.3 K Users
20 Questions 40 Marks 24 Mins
Start Now

Detailed Solution

Download Solution PDF

Carrier Lifetime (τ):

1) It is the interval from generation to recombination i.e. from breaking of the covalent bond until its recombination.

2) It is also the average lifetime of charge carriers.

\(L = \sqrt {D\tau } \)  ----(1)

Where L is called the length of diffusion which depends on charge carriers, mobility of carriers, carrier lifetime, and also temperature.

Diffusion length is the average length a carrier moves between generation and recombination. 

SI unit of L is cm.

Download Solution PDF
Latest UPSC IES Updates

Last updated on May 28, 2025

->  UPSC ESE admit card 2025 for the prelims exam has been released. 

-> The UPSC IES Prelims 2025 will be held on 8th June 2025.

-> The selection process includes a Prelims and a Mains Examination, followed by a Personality Test/Interview.

-> Candidates should attempt the UPSC IES mock tests to increase their efficiency. The UPSC IES previous year papers can be downloaded here.

More Carrier Diffusion Questions

Q1.The random motion of free electrons and holes due to thermal agitation is called
Q2.A p-type semiconductor with zero electric field is under illumination (low level injection) in steady state condition. Excess minority carrier density is zero at x = ±,2 ln where ln = 10-4 cm is the diffusion length of electrons. Assume electronic charge, q = −1.6 × 10-19 C. The profiles of photo-generation rate of carriers and the recombination rate of excess minority carriers (R) are shown. Under these conditions, the magnitude of the current density due to the photo-generated electrons at x = +2 ln is _________ mA/cm2 (rounded off to two decimal places).
Q3.The diffusion length for holes LP, is the 
Q4.The diffusion constant for holes in silicon is 13 cm2/s. What is the diffusion current if the gradient of the hole concentration \(\frac{dP}{dX} = -2 \times 10^{14}\) holes per cm3 per cm?
Q5.Assume electronic charge q = 1.6 × 10-19 C, kT/q = 25 mV and electron mobility μn = 1000 cm2/V-s. If the concentration gradient of electrons injected into a P-type silicon sample is 1 × 1021/cm4, the magnitude of electron diffusion current density (in A/cm2) is _________.
Q6.As shown, a uniformly doped Silicon (Si) bar of length L = 0.1 μm with a donor concentration ND = 1016 cm–3 is illuminated at x = 0 such that electron and hole pairs are generated at the rate of GL = \({G_{L0}}\left( {1 - \frac{x}{L}} \right),\;0 \le x \le L\), where GL0 = 1017 cm–3 s–1. Hole lifetime is 10–4 s, electronic charge q = 1.6 × 10–19 C, hole diffusion coefficient Dp = 100 cm2/s and low level injection condition prevails. Assuming a linearly decaying steady sate excess hole concentration that goes to 0 at x = L, the magnitude of the diffusion current density at x = L/2, in A/cm2, is ________.
Q7.An n-type silicon sample is uniformly illuminated with light which generates 1020 electron-hole pairs per cm3 per second. The minority carrier lifetime in the sample is 1μs in the steady state, the hole concentration in the sample is approximately 10x, where x is an integer. The value of x is

More Carrier Transport Questions

Q1.The resistivity of a uniformly doped n-type silicon sample is 0.50 Ω-cm. If the electron mobility (μn) is 1250 cm2/V-sec and the charge of an electron is 1.6 × 10-19 coulomb, the donor impurity concentration (ND) in the sample is
Q2.The random motion of free electrons and holes due to thermal agitation is called
Q3.In Hall effect, a difference voltage is produced _______ to electric current in the conductor, and to an applied _____ field perpendicular to the current.
Q4.The drift current is 200 mA and the diffusion current is 2 A. What is the total current in the semiconductor diode?
Q5.An n–type silicon sample of 10–3 m length and 10–10 m2 cross sectional area has an impurity concentration of 5 × 1020 atom/m3. If mobility of majority carries is 0.125 m2/v-sec, then the resistance of the sample will be ________.
Q6.If an electric field of 30 V/cm is applied across the specimen, then the drift velocity of free electron is ________. (Given µ = 34.8 × 10−4 m2/v-s)
Q7.The SI unit of conductivity is _________.
Q8.Which of the following carriers cause current in a semiconductor?
Q9.Calculate the hall voltage when the magnetic field is 8 A/m, current is 4 A, width is 5 m and the concentration of carrier is 1020.
Q10.A p-type semiconductor with zero electric field is under illumination (low level injection) in steady state condition. Excess minority carrier density is zero at x = ±,2 ln where ln = 10-4 cm is the diffusion length of electrons. Assume electronic charge, q = −1.6 × 10-19 C. The profiles of photo-generation rate of carriers and the recombination rate of excess minority carriers (R) are shown. Under these conditions, the magnitude of the current density due to the photo-generated electrons at x = +2 ln is _________ mA/cm2 (rounded off to two decimal places).
Crack GATE Electrical with
India's Super Teachers
Explore Supercoaching For FREE
Suggested Test Series
View All >
UPSC ESE (IES) Civil Mock Test Series
116 Total Tests with 1 Free Tests
Start Free Test
UPSC ESE (IES) Prelims Paper 1 Mock Test Series
54 Total Tests with   1 Free Tests
Start Free Test
Suggested Exams
Exam-Logo
UPSC IES

UPSC IES Important Links

More Electronic Devices Questions

Q1.In an n-type semiconductor, which of the following is true regarding the majority charge carriers?
Q2.A BJT is configured as a common-base amplifier; which of the following statements is INCORRECT?
Q3.For a diode operating in forward bias, which of the following statements is INCORRECT?
Q4.A Zener diode has a breakdown voltage of Vz = 7 V at 300 K, with a temperature coefficient of 2.3 mV/°C. What is the new breakdown voltage Vz at 400 K?
Q5.Identify the correct statement related to the P-N junction diode.
Q6.If mobility of electron is 𝑢𝑒and mobility of hole is 𝑢ℎ then
Q7.Compared to Photo lithography, Electron beam lithography results in : 
Q8.The dopants are introduced in the active areas of silicon by using which process ?
Q9.Conductivity of an extrinsic semiconductor is considerably influenced by : 
Q10.JFET is a:
Important Exams
Super Coaching
Exams
Test Series
Previous Year Papers
Objective Questions
Testbook USA SAT Exam
Testbook USA ACT Exam
US College Admissions Guide
Testbook Edu Solutions Pvt. Ltd.
1st & 2nd Floor, Zion Building,
Plot No. 273, Sector 10, Kharghar,
Navi Mumbai - 410210
[email protected]
Toll Free:1800 833 0800
Office Hours: 10 AM to 7 PM (all 7 days)
Company
About usCareers We are hiringTeach Online on TestbookPartnersMediaSitemap
Products
Test SeriesTestbook PassOnline CoursesOnline VideosPracticeBlogRefer & EarnBooks
Our Apps
Follow us on
Copyright © 2014-2022 Testbook Edu Solutions Pvt. Ltd.: All rights reserved
User PolicyTermsPrivacy
Get Free Access Now
Hot Links： teen patti master new version teen patti master purana teen patti master official teen patti cash game teen patti gold