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light-emitting diodes,” Appl. Phys. Lett 67, 1868 (1995). Georgia Tech •The shape of the “die” (chip) can greatly
aid light extraction by minimizing internal
ECE 3080 - Dr. Alan Doolittle EE 332 Spring 2013 Homojunction LED Design Considerations Homojunction LED Design Considerations
Homojunction LED Design Considerations
P-type GaP P-type GaP O Electron Current O F
Zn N-type GaP
N-type GaP Hole Current
•Efficient light generation results from Donor-Acceptor pair transition requires high
•Efficient light generation results from Donor-Acceptor pair transition – – requires high
doping level so Donor and acceptor are “close to each other”.
doping level so Donor and acceptor are “close to each other”. Georgia Tech E3080 - Dr. Alan Doolittle
ECE E 332 Spring 2013 How to HowWhite LEDs White
Make to Make Georgia Tech Slide Credit to Dr. Oliver Brandt, Ga Tech LEDs? EE 332 Spring 2013
ECE 3080 - Dr. Alan Doolittle Spontaneous Light Emission
Light Material Interaction •
• We can add to our understanding of absorption and spontaneous radiation due to
random recombination another form of radiation – Stimulated emission.
Stimulated emission can occur when we have a “population inversion”, i.e. when we
have injected so many minority carriers that in some regions there are more “excited
carriers” (electrons) than “ground state” carriers (holes).
Given an incident photon of the bandgap energy, a second photon will be “stimulated”
by the first photon resulting in two photons with the same energy (wavelength) and
This phase coherence results in minimal divergence of the optical beam resulting in a
directed light source.
EE 332 Spring 2013 Spontaneous vs Stimulated Light
Spontaneous vs Stimulated Light
Emission The power-current curve of a laser diode. Below threshold, the diode is anan LED. Above threshold, the
The power-current curve of a las...
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This document was uploaded on 02/18/2014.
- Spring '09