applied physics letters 93, 101112 (2008)
DESCRIPTION
The effect of the last quantum barrier on the internal quantum efficiency of InGaN-light emitting diode. Eun-Hyun Park, Jin Jang, Shalini Gupta, Ian Ferguson, Soo-Kun Jeon, Jae-Gu Lim, Jun-Serk Lee, Cheol-Hoi Kim, and Joong-Seo Park. APPLIED PHYSICS LETTERS 93, 101112 (2008). Y.C. Chiang. - PowerPoint PPT PresentationTRANSCRIPT
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Eun-Hyun Park, Jin Jang, Shalini Gupta, Ian Ferguson, Soo-Kun Jeon, Jae-Gu Lim, Jun-Serk Lee, Cheol-Hoi Kim, and Joong-Seo Park
The effect of the last quantum barrier on the internal quantum efficiency of InGaN-light emitting diode
APPLIED PHYSICS LETTERS 93, 101112 (2008)
Y.C. Chiang
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Outline
• Motive
• Experimental
• Results and Discussion
• Conclusions
• Extend discussion
• Reference
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Motive
Improvementin the internal quantum efficiency (IQE) is related low due to :strong piezoelectric field in MQWsHigh dislocation density by heterosubstrate
Unintentional Mg impurityMg-doped GaN profile :
deep acceptor activation process diffusion
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STUTSTUT OPTOELETRONICSOPTOELETRONICS && MICROWAVEMICROWAVE DEVICEDEVICE LABORATORYLABORATORY
Motive
Improvementin the internal quantum efficiency (IQE) is related low due to :strong piezoelectric field in MQWsHigh dislocation density by heterosubstrate
Unintentional Mg impurityMg-doped GaN profile :
deep acceptor activation process diffusion
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Experimental
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n-GaN
c-plane Sapphire
30nm-buffer layer
2μm-un-doped GaN
In0.27Ga0.73N/GaN
p-GaN
n-contact2μm n-GaN
ITO
p-contact
n~3E18/cm3
In0.3Ga0.7N/GaN
S1 : GaN-LQB (150 Å)
S2 : In0.03Ga0.97N/GaN LQB(150 Å)
Five periodsInGaN/GaN(20 Å/100 Å)
p~2E19/cm3
LQB x=0%,1.5%,3%,and 5%
chip size: 600 x 250 μm2
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Results and Discussion(1/5)
FIG. 1. Color online rms roughness(■) and V-shaped pit density(▲) MQWs as indium mole fraction of In(x)Ga(1−x)N-LQB.
LQB In含量提高使其較匹配Mg無法由 dislocation竄入井區
V-pit差異不大由 Mg濃度可看出無太大差別
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Ref. page 11
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Results and Discussion(2/5)
(b) 10x10 μm2 AFM surface images of MQWs with GaN-LQB. (c) In0.03Ga0.97N-LQB
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A simple schematic diagram to illustrate the growth mechanism: (a) As grown InGaN/GaN, (b) TMIn treatment and inter diffusion
① treading dislocations from the buffer layer
② strain relaxation associated with stacking faults on the surface ③ the embedded inclusions within large V-shaped defects that originate at the InGaN-to-GaN interface
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(c) Indium cluster remove, and (d) Indium as surfactant for the grow GaN barrier layer.
Smooth surface
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Results and Discussion(3/5)
FIG. 2. SIMS profiles of Mg and indium elements of LEDs with GaN-LQB S1 and In0.03Ga0.97N-LQB (S2).
Mg~1.2E19/cm3
來自 p-GaN diffusion
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Results and Discussion(4/5)
FIG. 2. SIMS profiles of Mg and indium elements of LEDs with GaN-LQB S1 and In0.03Ga0.97N-LQB (S2).
5.8E17/cm3
3.8E18/cm3
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Back
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Results and Discussion(5/5)
(b) PL and EL (chip size: 600 x 250 μm2 at 20 mA) (c) spectra of S1(■) and S2(▲) .
S2 High than S1 72% S2 High than S1 15%
不確定是在哪個井區發光,為了要區別所以另外做 475nm
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Deep-Level
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深層能階
淺層能階
淺層能階
Back
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A high indium contained LQB made smoother surface of MQWs and shaper interface between MQWs and P-GaN layer by the surfactant role of indium.
A high indium contained LQB could drop the IQE of LED due to the increase in electron overflow to the p-GaN. Reducing unintentional Mg impurity diffusion into an active layer
would be more important.
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Conclusions
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Extend discussion
當銦含量逐漸提高,為何使鎂擴散情況降低 ?猜測:因為 LQB 的銦↑使其和 well 的不匹配情形稍微降低,也因此 dislocation density 也相對降低,導致鎂比較沒辦法藉由這些缺陷進入到井區。
銦含量提高使 MQWs 表面平整的真正製程原因 ?( 不詳 )
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References
• Eun-Hyun Park, Jin Jang, Shalini Gupta, Ian Ferguson, Soo-Kun Jeon, Jae-Gu Lim, Jun-Serk Lee, Cheol-Hoi Kim, and Joong-Seo Park, “The effect of the last quantum barrier on the internal quantum efficiency of InGaN-light emitting diode,” APPLIED PHYSICS LETTERS 93, 101112 (2008).
• 史光國 編譯 , “ 現代半導體發光及雷射二極體材料技術 ,” 全華科技圖書股份有限公司 , 2004.
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