Gentle Intro to Semiconductors ENGN/PHYS 207. The ubiquitous LED.
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Transcript of Gentle Intro to Semiconductors ENGN/PHYS 207. The ubiquitous LED.
Gentle Intro to Semiconductors
ENGN/PHYS 207
The ubiquitous LED
Collection of diodes
Diode = electronic valve
Forward bias: Current flows! Reverse bias: No current flow!
The Silicon Valley
Warm-up question(s)
What does it mean for a material to be able to “conduct” electricity?
Pure silicon lattice(intrinsic semiconductor)
2D lattice model showing covalent bonds in Si crystal
Band Theory of SolidsQuantum Mechanics: Energy levels occupied by
electrons are discrete. Amphitheatre analogy
Aspendos Theatre, Turkey
Conduction Band
Band gap
Valence Band
Energy Level Diagrams
Electron-Hole Pairs (EHPs)
Wait—what’s a hole?
Vacancy in the valence bandActs like mobile positive chargeAn electron can fall into a hole
(Recombination)
Important Fact Thermal energy to move and shake around a lattice at (T
= 300K)
kT = 1/40 eV = 0.025 eV
Why pure silicon isn’t so hot
Large energy barrier!
Let’s dope up (?)
III (extra hole)
IV
V (extra e-)
Group Number
That’s dope: N and P type
N-type: Extra electrons P-type: Extra holes
Dopant electrons and holes are mobileNuclei locked in the lattice, they are NOT mobile.
Why doping is actually good for us
N-type: easily donates electrons into conduction band
P-type: easily accepts electrons into valence band
The PN junction
The Diode Equation
VB
I
Silicon Diodes as Rectifiers
“Electronic Valve” action
Current can essentially flow in one direction only
Reverse bias Forward bias
0.7 V
Let there be Light…
Idealized LED turn-on voltages
VF (volts)
I (mA)
1.8V 3.5V 3.6V
A bright idea—2014 Nobel prize for the blue LED
Isamu Akasaki Hiroshi Amano Shuji Nakamura
Sources
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