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

Compute the number of electrons that pass a given point, Q A wire with n = ...

Q A wire with n = 10 30 electrons/m 3 has an area of cross section A = 1mm 2 and carries a current i = 50 mA. Compute the number of electrons that pass a given point in 1 s, and

Service standards and agricultural users, Service standards: The forum...

Service standards: The forum of regulators (constituted through the central government for consistency in regulation in the area of distribution) will decide the basic framewo

Explain the construction of depletion mosfet, Q. Explain the construction o...

Q. Explain the construction of depletion MOSFET? A slab of p-type material is formed from a silicon base and it is referred to as the substrate. It is the foundation upon which

Determine the current and voltage in given network, Q. For a part of the ne...

Q. For a part of the network shown in Figure, given that i 1 = 4A; i 3 (t) = 5e -t , and i 4 (t) = 10 cos 2t, find v 1 , v 2 , v 3 , v 4 , i 2 , and i 5 .

Complex programmable logic device, The small electronics consultancy compan...

The small electronics consultancy company that you work for has been commissioned to design a portable mixed signal heart rate monitor unit for the National Health Service. You hav

Explain nodes analysis, Nodes analysis Analysis using KCL to solve for ...

Nodes analysis Analysis using KCL to solve for voltages at every common node of the network and as determines the currents by and voltages across every elements of the network.

Difference between cmp and sub instructions, Mention how do the following i...

Mention how do the following instructions differ in their functionality SUB: It performs changes the destination operand and the subtraction operation. CMP: Comparison instr

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