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This gives the tutorial sheet on Chapter 2-Semiconductor Physics.

Tutorial Sheet of Chapter 2.Semiconductor Physics.

Question 1. (a)Determine the Drift Velocity of electron and hole in the given intrinsic sample in Figure-Tutorial 2.1. with 10V applied across the junction?[vdrift(n)=5800cm/s,vdrift(p)=1800cm/s]Assume mobility given for intrinsic sample.

(b)Determine the conductivity of the following intrinsic sample?[σ=3*10 -6 S/cm]

(b) Determine the current flowing though the intrinsic sample?[0.72microA]

Question 2. The energy-band diagram is given in Figure-Tutorial2.2.

  1. Calculate the probability of occupancy at Ed according to Fermi-Dirac Statistics? [P(Ed)=1.41%]
  2. Calculate the % of ionization of Donor Atoms ? [99%]
  3. If N C = effective density of states at E C = 3.01×10 19 /cc then calculate n n - ? [6.3917×10 16 /cc]
  4. Calculate p n - if N V = effective density of states at E V = 1.04×10 19 /cc ? [2773.81]
  5. Calculate n i 2 ? [(1.15×10 10 ) 2 ]
  6. Calculate N D [6.3917×10 16 /cc ]

Question 3 .In a P-Type material, E F -E V = 0.1 eV and E a -E V =0.045eV.

Calculate the % of ionization of Acceptor Atoms ? [89%]

Question 4 .There is a compensated P-Type material at 300K. Minority carrier concentration is measured to be n p - =10 6 /cc. Acceptor Dopent Concentration = 10 15 /cc.

  1. Determine majority carrier concentration? [10 14 /cc].
  2. Determine N d ?[9×10 14 /cc].
  3. Determine the total scattering centers.[ 19×10 14 /cc ].

Question 5. In Copper, resistivity= ρ = 1.67×10 -8 Ω-m and conductivity = σ = 6×10 7 S/m=qμn and n=8.5×10 22 /m 3 . Determine electron mobility ? [40 cm 2 /(V-s) ]

Question 6. In a 3 m long Cu Wire R = 0.03Ω and I = 15A through the wire.

  1. Determine V drop across the wire ? [0.45V]
  2. Determine E along the z-axis ? [0.15V/m]
  3. Determine drift velocity of electron if μ= 40 cm 2 /(V-s)? [0.6×10 -3 m/s]
  4. Determine the Fermi-velocity of conducting electron ? [10 6 m/s]
  5. Determine the mean free time between two scatterings also defined as relaxation time ? [2.27×10 -14 s]
  6. Determine the mean free path ?[275A°]. Compare this with lattice constant a =3.6A°.

Question 7. Typical N-Type resistivity ρ S =1Ω-cm.Typical current density 100A/cm 2 . mobility of electrons=1000cm 2 /V-s

  1. Calculate E ? [100V/cm]
  2. Calculate drift velocity ? [1.0×10 5 cm/s]

Question 8 .In a P-Type Sample , E=10 3 V/cm is applied. Determine drift velocity, mean free time and mean free path ? Assume μ p = 470 cm 2 /(V-s).

[Drift velocity = 4.7×10 5 cm/s which is much lower than thermal velocity of holes=2.2×10 7 cm/s; τ = 0.1ps, Mean Free Path = 220A°]

Question 9. The effective mass of electron and hole in semi-conductor is different from the mass in free space . Why?

The electrons and holes in a crystal interact with the periodic Coulombic Field in the Crystal. They surf over the periodic potential variation of the crystal lattice in the process developing roller coaster effect which leads to drastic reduction in effective mass.

Si Ge GaAs InAs AlAs
m n /m 0 0.26 0.12 0.068 0.023 2.0
m p /m 0 0.39 0.30 0.50 0.30 0.3

m n /m 0 = effective mass of electron/free space mass of electron

m p /m 0 = effective mass of hole/free space mass of hole.

In Silicon, using the effective mass of electron and holes the thermal velocity = 2.5×10 7 cm/s. Scatter Limit Velocities of electron and hole are of the same order.

Questions & Answers

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Akash Reply
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s. Reply
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Devang Reply
are you nano engineer ?
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Mostly, they use nano carbon for electronics and for materials to be strengthened.
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s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
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s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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Damian Reply
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I start with an easy one. carbon nanotubes woven into a long filament like a string
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Sravani Reply
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preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
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what is the application of nanotechnology?
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
anybody can imagine what will be happen after 100 years from now in nano tech world
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
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silver nanoparticles could handle the job?
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I'm interested in Nanotube
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
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Prasenjit Reply
how did you get the value of 2000N.What calculations are needed to arrive at it
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Source:  OpenStax, Solid state physics and devices-the harbinger of third wave of civilization. OpenStax CNX. Sep 15, 2014 Download for free at http://legacy.cnx.org/content/col11170/1.89
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