1 / 25

Lecture 5.0

Lecture 5.0. Properties of Semiconductors. Importance to Silicon Chips. Size of devices Doping thickness/size Depletion Zone Size Electron Tunneling dimension Chip Cooling- Device Density Heat Capacity Thermal Conductivity. Band theory of Semiconductors. Forbidden Zone – ENERGY GAP.

Download Presentation

Lecture 5.0

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. Lecture 5.0 Properties of Semiconductors

  2. Importance to Silicon Chips • Size of devices • Doping thickness/size • Depletion Zone Size • Electron Tunneling dimension • Chip Cooling- Device Density • Heat Capacity • Thermal Conductivity

  3. Band theory of Semiconductors • Forbidden Zone – ENERGY GAP Conduction Band Valence Band

  4. Silicon Band Structure - [Ne]3s23p2

  5. Fermi-Dirac Probability Distribution for electron energy, E • Probability, F(E)= • (e{[E-Ef]/kBT}+1)-1 • Ef is the • Fermi Energy

  6. Number of Occupied States Density of States Fermi-Dirac T>0

  7. Difference between Semiconductors and Insulators kBT =0.0257 eV at 298˚K

  8. Probability of electrons in Conduction Band • Lowest Energy in CB • E-Ef Eg/2 • Probability in CB • F(E)= (exp{[E-Ef]/kBT} +1)-1 ) • = (exp{Eg/2kBT} +1)-1 •  exp{-Eg/2kBT} for Eg>1 eV @ 298K kBT =0.0257 eV at 298˚K

  9. Variation of Conductivity with T =d/dT

  10. Intrinsic Conductivity of Semiconductor • Charge Carriers • Electrons • Holes • = ne e e + nh e h • # electrons = # holes •   ne e (e+ h) • ne  C exp{-Eg/2kBT} ne=2(2 m*e kBT/h2)3/2 exp(-Eg /(2kBT)) Ef=Eg/2+3/4kBT ln(m*h/m*e)

  11. Mobilities

  12. Semiconductor Photoelectric Effect • Light Absorption/Light Emission (photodetector)/(photo diode laser) • Absorption max=hc/Eg

  13. Light Emitting Diode

  14. Photodiode Laser • Color depends on band gap, Eg •  =hc/Eg Eg>3.0 transparent Pb 0.37 0.27 0.33 IR detectors

  15. Diode Laser

  16. Extrinsic Conductivity of Semiconductor • Donor Doping Acceptor Doping • n-type p-type p= 2(2 m*h kBT/h2)3/2 exp(-Ef/kBT) N=nd+ni Law of Mass Action, Nipi=ndpd or =nndn

  17. Extrinsic Conductivity of Semiconductor • Donor Doping Acceptor Doping

  18. Electron Density • Dopant Concentration effects • Electron Density • Electrical Conductivity

  19. Conductivity • Intrinsic Range • Exponential with T • Extrinsic Range • Promoted to CB •   • Decreasing ,  • Joins Intrinsic   • Majority/minority Carriers • = ne e e + nh e h

  20. Majority/minority Carriers • Conductivity • = ne e e + nh e h • n-type ne>>nh • Low number of holes due to recombination. • Law of Mass Action • Nipi=ndpd • (For p-type Nipi =nndn )

  21. Extrinsic Conductivity of Semiconductor • Donor Doping Acceptor Doping • n-type p-type Ed = -m*e e4/(8 (o)2 h2) Ef=Eg-Ed/2 Ef=Eg+Ea/2

  22. Effective Mass • Holes • Electrons

  23. Wafer Sales • Following PRIME GRADE Si wafers are all single-side polish $14.50 each for 25 wafers each $11.00 for 50 or more (we can double side polish) • 4" P<111> 3.0-6.6 ohm-cm • 4" N<100> 4.0-6.0 ohm-cm • 4" P<111> 7.0-21.6 ohm-cm • 4" P<100> 12.0-16.0 ohm-cm • 4" P<111> 3.0-5.0 ohm-cm • http://www.collegewafer.com/

  24. GaP Wafer 2" Undoped (100) $180.00 each 2" S doped (111) $180.00 each

  25. C&ENews 1/6/03

More Related