Intrinsic material, Electrical Engineering

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).
Posted Date: 1/11/2013 4:42:03 AM | Location : United States







Related Discussions:- Intrinsic material, Assignment Help, Ask Question on Intrinsic material, Get Answer, Expert's Help, Intrinsic material Discussions

Write discussion on Intrinsic material
Your posts are moderated
Related Questions
Bipolar Junction Transistor: Transistor construction: the emitter layer is heavily doped, the base is light doped and the collector is only lightly doped. Outer layer has wi

Question: a) For the circuit shown in figure (i) Determine the voltages across R1 and R2 and (ii) Determine the current which flows across R1 and R2. Both D1 and D2 a


For carry Flag JC (  jump on  Carry ) and JNC (Jump  on No carry ) Instructions : JC transfer the  execution of the  program to the  specified memory  address if  carry

Q. The flux in a magnetic core is alternating sinusoidally at a frequency of 500 Hz. The maximum flux density is 1 T. The eddy-current loss then amounts to 15W. Compute the eddy-cu

Mesh analysis procedure : 1.  Assign a distinct current to every closed loop of the network. 2.  Apply KVL around every closed loop of the network. 3.  Solve the resulting

Q. A rectangular air-?lled RG-52/U is made of brass (ρ = 3.9 × 10-8 m) and has dimensions a = 22.86 mm and b = 10.16 mm. (a) Determine ¯ Z0(= R0) at the limits of the practica

Task a)    Investigate and describe the significance of the following: i.    Slenderness ratio and buckling in columns ii.    Effective length of columns b) Explain Eu

Semiconductor Diode: the semi conductor diode is formed by simply bringing n and p tripe material together (constructed from same base ge and si), at the instant the two mater

Q. An antenna with an effective noise temperature of 130 K couples through a waveguide that has a loss of 0.8 dB to a receiver. Find the effective noise temperature presented by th