APPLIED PHYSICS LETTERS 93, 101112 (2008)

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STUTSTUT 　　 OPTOELETRONICSOPTOELETRONICS 　　 && 　　 MICROWAVEMICROWAVE 　　 DEVICEDEVICE 　　LABORATORYLABORATORY

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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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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(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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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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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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(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

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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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APPLIED PHYSICS LETTERS 93, 101112 (2008)

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