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

Performance of digital modulation schemes, Hello, Please how do I compare p...

Hello, Please how do I compare performance of a digital modulation scheme with matlab?

DC motor and DC generator, write down the similarities between motors and g...

write down the similarities between motors and generators

Security alarm system, In this Project you will simulate a Security Alarm s...

In this Project you will simulate a Security Alarm system using the Quick flash board. A switch is placed as shown in the figure below. The main goal of this project is: Task 1:

Explain the construction of synchronous machines, Explain the Construction ...

Explain the Construction of Synchronous Machines? Basically all synchronous machines require a DC excited field winding in order to produce magnetic flux. For majority of machi

Buck converter - power supplies , Buck Converter In buck  converters th...

Buck Converter In buck  converters the output  voltage is  always  less than the  input  voltage. The basic  circuit  of buck converter is shown  in figure. The operation of th

Explain polling, What is meant by polling? In polling schemes, a set of...

What is meant by polling? In polling schemes, a set of address lines is driven by the controller to address every of the masters in sequence. When a bus request is received fro

Ac voltage controllers, Q. Explain AC voltage controllers? Common appli...

Q. Explain AC voltage controllers? Common applications for these controllers are found in fan, pump, and crane drives. Figure shows three-phase symmetrical ac voltage-controlle

Explain mobility, Explain Mobility . Average drift velocity of electrons...

Explain Mobility . Average drift velocity of electrons (e - ) in an applied field is proportional to the field, the absolute magnitude of the proportionality factor eq/m, termed

Charging of the capacitor, Charging of the capacitor: Considering the ...

Charging of the capacitor: Considering the below diagram, with slight approximation the ripple voltage can be supposed as triangular. To the cut-out point from the cut-in poin

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