16. semiconductor photon sources - hanyangoptics.hanyang.ac.kr/~shsong/p16-semiconductor...
TRANSCRIPT
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16. Semiconductor Photon Sources
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Electroluminescence devices
Light-emitting diode Semiconductor Laser diode(LED) Semiconductor
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 Photometryradiometry photometry
watt (W)W/ 2
lumen (lm) l (l )
Radiant flux :I di
: Luminous fluxW/m2
W/srW/(sr.m2)
lux (lx)candela (cd)Cd/m2
Irradiance :Radiant intensity :
Radiance :
: illuminance : luminous intensity: luminance
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CIE (International Commission on Illumination)Luminous Efficiency curve555 nm Radiant flux
of 1 Watt at 555 nm is the luminous flux
Luminous Efficiency curve
the luminous fluxof 685 lm (lumen)
Radiant flux of 1 Watt at 610 nm is
th l i fl610 nm
Luminous efficiency V(λ)
the luminous fluxof 342.5 lm (lumen)
610 nm
Photometric unit=
685 x V(λ) x radiometric unit685 x V(λ) x radiometric unit
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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증명!Exercise 17 1-3Exercise 17.1-3
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LED characteristics
Internal efficiencyInternal efficiency
Extraction efficiency
External efficiency
Power-conversion efficiency (or, wall-plug efficiency)
[ ] power ext extP h for h eVIV eV
νη η η ν= = ≈ ≈
Luminous efficiency (lm/W)
{ } { }/ 685 ( ) 685 ( )lm W extP hV VIV eV
νη λ η λ= × = ×
Luminous efficiency (lm/W)
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Extraction efficiency
( )ic dθ
φ φ∫ ( )0
2
2 sin
2 (1 cos )
c
c
A r rd
r
π φ φ
π θ
=
= −
∫
241
extractAr
ηπ
=
2
1 (1 cos )21 (1 1 1/ )
c
n
θ= −
= − −
2
(1 1 1/ )21
4
n
n
= − −
≈
1.9 % for 3.6 (GaAs)extract nη ≈ =
4n
4 % for 2.5 (GaN)extract
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
Baba
Limited by surface recombination
Good scheme!!!
Limited by surface recombination
Good scheme!!!
Lumiled
100 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%)Needed (>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 lightingNot 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)OLED는 유기물(단분자/저분자 또는 고분자) 박막에 양극과 음극을 통하여 주입된 전자와 정공이 재결합하여 여기자를 형성하고, 형성된 여기자로 부터의 에너지에 의해 특정한 파장의 빛이 발생하는 현상을 이용한자체 발광형 디스플레이 소자.
• 자체 발광형. (어두운 곳이나 외부의 빛이 들어 올 때도 시인성이 좋은 특성을 갖음.)
• 넓은 시야각 (일반 브라운관 같이 바로 옆에서 보아도 화질이 변하지 않음 )• 넓은 시야각. (일반 브라운관 같이 바로 옆에서 보아도 화질이 변하지 않음.)
• 빠른 응답속도. 텔레비전 화면 수준의 동화상 재생에도 자연스러운 영상을 표현. (LCD의 약 1,000배 )
• 초박, 저전력. 백라이트라 필요 없기 때문에 저소비전력(약 LCD의 ½ )과 초박형(약 LCD의 1/3 )이 가능.
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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 제품
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But, OLEDs are …
• Life time – blue organics have shorter life time compared to red and green• Manufacturing - expensiveg p• Moisture can damage OLED
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Resonant-cavity LEDs (RC-LEDs)
RCLED spectrum
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Semiconductor optical amplifiers (SOA)
forward-biasedheavily dopedp-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 carrierconcentration Narrower
active region (l)
(Double)Heterostructures
active region (l)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