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

Forces and torques in magnetic-field systems, Q. Forces and torques in magn...

Q. Forces and torques in magnetic-field systems? We mentioned earlier that the greater ease of storing energy in magnetic fields largely accounts for the common use of electrom

Briefly explain the principle and operation of strain gauges, Question: ...

Question: (a) With the help of a clearly labeled diagram explain the functioning of a basic thermocouple. (b) Briefly explain the principle and operation of strain gauges

What do you mean by capacitance, Q. What do you mean by Capacitance? An...

Q. What do you mean by Capacitance? An ideal capacitor is an energy-storage circuit element (with no loss associated with it) representing the electric-field effect. The capaci

Triac - power semiconductor devices , Triac  As the  name  suggests T...

Triac  As the  name  suggests TRIAC  is advice which  has three  electrodes and works  on AC.  The three terminals of triac are MTI ( Main Terminal ) MT2 ( Main  terminal ) an

List out the five categories of the 8085 instructions, List out the five ca...

List out the five categories of the 8085 instructions. Give examples of the instructions for each group. 1.  Data transfer group - MOV, MVI, LXI. 2.  Arithmetic group - ADD,

Congestion, It is uneconomic to provide adequate equipment to carry all the...

It is uneconomic to provide adequate equipment to carry all the traffic which could possibly be offered to a telecommunication system. In a telephone exchange it's theoretically po

A, A microstrip antenna system operating at 915MHz must be designed using R...

A microstrip antenna system operating at 915MHz must be designed using Rogers RO3010 substrate with the thickness of 0.635mm.

Discuss stepper motor interfaced to the 82c55, Discuss Stepper motor interf...

Discuss Stepper motor interfaced to the 82C55. A stepper motor rotates into steps in response to digital pulse input. There shaft of the motor rotates in equivalent increments

Explain direct data addressing mode, Direct data addressing mode (with exam...

Direct data addressing mode (with examples) available in microprocessors. Direct Mode: Instruction comprises memory access. CPU accesses which location into memo

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