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Gentle Intro to Semiconductors

Explore the fascinating world of semiconductors and diodes in this comprehensive introduction to the principles of electricity conduction. Learn about the behavior of pure silicon, the significance of doping with N-type and P-type materials, and the construction of PN junctions. Discover how LEDs (light-emitting diodes) work, from energy band theory to the exciting advances that led to the development of blue LEDs, recognized by the Nobel Prize. This resource is essential for anyone interested in electronics and photonics.

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Gentle Intro to Semiconductors

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  1. Gentle Intro to Semiconductors ENGN/PHYS 207

  2. The ubiquitous LED

  3. Collection of diodes

  4. Diode = electronic valve Forward bias: Current flows! Reverse bias: No current flow!

  5. The Silicon Valley

  6. Warm-up question(s) • What does it mean for a material to be able to “conduct” electricity?

  7. Pure silicon lattice(intrinsic semiconductor) 2D lattice model showing covalent bonds in Si crystal

  8. Band Theory of Solids • Quantum Mechanics: Energy levels occupied by electrons are discrete. • Amphitheatre analogy Conduction Band Band gap Valence Band Aspendos Theatre, Turkey

  9. Energy Level Diagrams

  10. Electron-Hole Pairs (EHPs)

  11. Vacancy in the valence band • Acts like mobile positive charge • An electron can fall into a hole (Recombination) Wait—what’s a hole?

  12. Thermal energy to move and shake around a lattice at (T = 300K) kT =1/40 eV = 0.025 eV Important Fact

  13. Large energy barrier! Why pure silicon isn’t so hot

  14. Let’s dope up (?) Group Number III (extra hole) IV V (extra e-)

  15. N-type: Extra electrons P-type: Extra holes That’s dope: N and P type Dopant electrons and holes are mobile Nuclei lockedin the lattice, they are NOT mobile.

  16. N-type: easily donates electrons into conduction band P-type: easily accepts electrons into valence band Why doping is actually good for us

  17. The PN junction

  18. I VB The Diode Equation

  19. Silicon Diodes as Rectifiers • “Electronic Valve” action • Current can essentially flow in one direction only 0.7 V Reverse bias Forward bias

  20. Let there be Light…

  21. Rainbow of Fruit Flavors

  22. Idealized LED turn-on voltages I(mA) 1.8V 3.5V 3.6V VF (volts)

  23. A bright idea—2014 Nobel prize for the blue LED Isamu Akasaki Hiroshi Amano Shuji Nakamura

  24. Images: • http://49chevy.blogs.com/fusor/2008/10/fun-with-electr.html • http://www-inst.eecs.berkeley.edu/~ee143/sp06/lectures/Semiconductor_tutorial.pdf • http://www.allaboutcircuits.com/vol_3/chpt_2/3.html • http://free-zg.t-com.hr/Julijan-Sribar/preview/vol1.html • http://www.launc.tased.edu.au/online/sciences/Physics/photonics/bias.htm • http://www.mtmscientific.com/diodes.html • http://www.mpoweruk.com/semiconductors.htm • http://free-zg.t-com.hr/Julijan-Sribar/preview/vol1.html • http://electrons.wikidot.com/methods-for-the-determination-of-ground-state-wavefunction • http://www.electronics-tutorials.ws/diode/diode_8.html • http://www.nobelprize.org/nobel_prizes/physics/laureates/2014/press.html Animations: • http://pvcdrom.pveducation.org/SEMICON/PN.HTM • http://www.acsu.buffalo.edu/~wie/applet/students/jiawang/pn.html • http://www.youtube.com/watch?v=O3x7NdUuu0Q&feature=related • http://www.youtube.com/watch?v=DbjR-2knrpo Sources

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