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7/27/2019 P16-Semiconductor Photon Sources
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16. Semiconductor Photon Sources
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Electroluminescence devices
Light-emitting diode Laser diode(LED)
optical amplifier
(SOA)
(LD)
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Evolution of Lighting to LEDs
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LUX (lx)?, LUMEN (lm)?, CANDELA (cd)?
Table 19-1Radiometry and Photometry
radiometry photometry
watt (W) lumen (lm)Radiant flux : : Luminous fluxm
W/srW/(sr.m2)
ux x
candela (cd)Cd/m2
rra ance :
Radiant intensity :Radiance :
: illuminance
: luminous intensity: luminance
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CIE (International Commission on Illumination)
555 nmRadiant f lux
of 1 Watt at 555 nm isthe luminous f lux
of 685 lm (lumen)
Radiant f luxof 1 Watt at 610 nm is
610 nm
Luminous efficiency V()
e um nous ux
of 342.5 lm (lumen)
Photometric uni t
=
Ex) 100 lm/W means,
At Green ~ 100/680 ~ 15 %
At Blue/Red ~ 100/340 ~ 30%
(If QE ~ 100%)
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Semiconductor Light for Visualization
Osram SID 2004
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Semiconductor Light for Illumination
Osram SID 2004
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LED Roadmap for Automotive
Osram SID 2004
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LED characteristics
+
-
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Forward voltage for LEDs
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!-.
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LED characteristics
Internal efficienc
Extraction efficiency
External efficiency
Power-conversion efficiency (or, wall-plug efficiency)
[ ]power ext extP h
for h eVIV eV
= =
Luminous efficienc lm/W
{ } { }/ 685 ( ) 685 ( )lm W ext P hV VIV eV
= =
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Extraction efficiency
0
2
2 s n
2 (1 cos )c
r r
r
=
=
24extract
r
=
2
(1 cos )2
1
c=
2
2
1
1.9 % for 3.6 (GaAs)extract
n =
n
4 % for 2.5 (GaN)n =
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Extraction efficiency
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Spatial pattern of emitted light
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Extraction efficiency
Photonic Crystal-LEDs
BabaLimited by surface recombination
Good scheme!!!
Limited by surface recombination
Good scheme!!!
Lumiled100 um device size achievable.
Several layer of PC for extraction.Good internal quantum efficiency
N d d ( 90%)
100 um device size achievable.Several layer of PC for extraction.Good internal quantum efficiency
N d d ( 90%)eeded (>90%).Multiple pass limits device size (~10um).
Small volume needed.Not so good for lighting
Needed (>90%).Multiple pass limits device size (~10um).
Small volume needed.Not so good for lightingot so good for lighting.
Surface recombination limited
Surface recombination limited.
Not so good for lighting.Surface recombination limited
Surface recombination limited.
Noda
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OLED (Organic Light Emitting Diode)
OLED (/ ) , .
. ( .) . .
. . (LCD 1,000 ) , . ( LCD ) ( LCD 1/3 ) .
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OLED Structure
100 500 nanometers thick
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Organic LEDs (OLEDs)
Discovered by Ching Tang and Van Slyke at Eastman Kodak in 1987.
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OLED
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But, OLEDs are
Life time blue organics have shorter li fe time compared to red and green
Manufacturing - expensive
Moisture can damage OLED
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Resonant-cavity LEDs (RC-LEDs)
RCLED spectrum
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Semiconductor optical amplifiers (SOA)
forward-biased
heavily doped
p-n junction
If the intraband relaxation time is much shorter than the interband relaxation time,
a steady-state population inversion between the bands may be established.
Optical Pumping Electric-Current Pumping
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Heterostrctures
Injected carrier
concentration Narrower
(Double)Heterostructures
is important
l
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Microcavity lasers
VCSEL
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Quantum Cascade Lasers
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QCL
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QCL
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QCL
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QCL