Intrinsic material, Electrical Engineering

Assignment Help:

Intrinsic Material

  1. A perfect semiconductor crystal with no impurities or lattice defects.
  2. No carriers at 0 K, since the valence band is completely full and the conduction band is completely empty.
  3. For T > 0 K, electrons are thermally excited from the valence band to the conduction band (EHP generation).
  4. EHP generation takes place due to breaking of covalent bonds => required energy = Eg.
  5. The excited electron becomes free and leaves behind an empty state (hole).
  6. Since these carriers are created in pairs, the electron concentration (n/cm3) is always equal to the hole concentration (p/cm3), and each of these is commonly referred to as the intrinsic carrier concentration (ni).
  7. Thus, for intrinsic material n = p = ni.
  8. These carriers are not localized in the lattice; instead they spread out over several lattice spacings, and are given by quantum mechanical probability distributions.
  9. Note: ni = f (T).
  10. To maintain a steady-state carrier concentration, the carriers must also recombine at the same rate at which they are generated.
  11. Recombination occurs when an electron from the conduction band makes a transition (direct or indirect) to an empty state in the valence band, thus annihilating the pair.
  12. At equilibrium, ri =gi, where gi and ri are the generation and recombination rates respectively, and both of these are temperature dependent.
  13. gi(T) increases with temperature, and a new carrier concentration ni is established, such that the higher recombination rate ri(T) just balances generation.
  14. At any temperature, the rate of recombination is proportional to the equilibrium concentration of electrons and holes, and can be given by ri= αrn0p0 = αrni2=gi(5) where αris a constant of proportionality (depends on the mechanism by which recombination takes place).

Related Discussions:- Intrinsic material

Cro, role of trigger circuit in cro

role of trigger circuit in cro

Determine the resultant mmf, Q. The N-coil windings of a three-phase, two-p...

Q. The N-coil windings of a three-phase, two-pole machine are supplied with currents ia,ib, and ic, which producemmfs given by F a = Ni a cos θm; F b = Ni b cos(θm - 120°); and

Electromagnetic torque, The torque produced by each conductor in the field ...

The torque produced by each conductor in the field will be:  where A is the area of the armature winding in the magnetic field, Ia is the current in armature winding, and B

Write a note on clampers, Q. Write a note on clampers ? Clamper is a ci...

Q. Write a note on clampers ? Clamper is a circuit that "clamps" a signal to a different dc level. The different types of clampers are positive negative and biased clampers.

Describe the magnetic effects of current, 1.   Describe the magnetic effe...

1.   Describe the magnetic effects of current? ( to achieve a pass grade, describe the magnetic effect of current) 2.   Complete the diagram to show the direction of mo

Determine the transfer functions, The Ward-Leonard system, which is used in...

The Ward-Leonard system, which is used in the control of large dc motors employed in rolling mills, is a highly flexible arrangement for effecting position and speed control of a s

Magnetic circuits, Magnetic circuits To  see  how  this   is  used   i...

Magnetic circuits To  see  how  this   is  used   in  practice, consider a coil of N turns wound onto a closed ring shaped former with a very high (note:    r (steel) = 200

Determine the transfer function c/r for the block diagram, Feedback amplifi...

Feedback amplifiers are of great importance in electronic circuits. The block diagram of a class of feedback amplifier is shown in Figure. Determine the transfer function C/R for t

Power semiconductor-controlled drives, Q. Explain Power semiconductor-contr...

Q. Explain Power semiconductor-controlled drives? Power electronics deals with the applications of solid-state electronics for the control and conversion of electric power. Con

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd