1. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 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

2. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Outline Motive Experimental Results and Discussion Conclusions Extend discussion Reference 2

3. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Motive  Improvementin the internal quantum efficiency (IQE) is related low due to ： strong piezoelectric field in MQWs High dislocation density by heterosubstrate  Unintentional Mg impurity  Mg-doped GaN profile ： deep acceptor deep acceptor activation process diffusion 3

4. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Motive  Improvementin the internal quantum efficiency (IQE) is related low due to ： strong piezoelectric field in MQWs High dislocation density by heterosubstrate  Unintentional Mg impurity  Mg-doped GaN profile ： deep acceptor deep acceptor activation process diffusion 4

5. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Experimental 5 n-GaN c-plane Sapphire 30nm-buffer layer 2μm-un-doped GaN In 0.27 Ga 0.73 N/GaN p-GaN n-contact 2μm n-GaN ITO p-contact n~3E18/cm 3 In 0.3 Ga 0.7 N/GaN S1 ： GaN-LQB (150 Å) S2 ： In 0.03 Ga 0.97 N/GaN LQB( 150 Å ) Five periods InGaN/GaN(20 Å/100 Å) p~2E19/cm 3 LQB x=0%,1.5%,3%,and 5% chip size: 600 x 250 μm 2

6. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 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 6 Ref. page 11

7. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Results and Discussion(2/5) (b) 10x10 μm 2 AFM surface images of MQWs with GaN-LQB. (c) In 0.03 Ga 0.97 N-LQB 7

8. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 8  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

9. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 9 (c) Indium cluster remove, and (d) Indium as surfactant for the grow GaN barrier layer. Smooth surface

10. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Results and Discussion(3/5) FIG. 2. SIMS profiles of Mg and indium elements of LEDs with GaN-LQB S1 and In 0.03 Ga 0.97 N-LQB (S2). Mg~1.2E19/cm 3 來自 p-GaN diffusion 10

11. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Results and Discussion(4/5) FIG. 2. SIMS profiles of Mg and indium elements of LEDs with GaN-LQB S1 and In 0.03 Ga 0.97 N-LQB (S2). 5.8E17/cm 3 3.8E18/cm 3 11 Back

12. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Results and Discussion(5/5) (b) PL and EL (chip size: 600 x 250 μm 2 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 12

13. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY Deep-Level 13 深層能階 淺層能階 Back

14. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY  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. 14 Conclusions

15. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 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 ) 15

16. www.omdl.tw STUT OPTOELETRONICS & MICROWAVE DEVICE LABORATORY 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. 16