專題研討 ( 二 ) Electron-Blocking-Layer, n-EBL Hole-Blocking-Layer, HBL 碩研電子一甲 MA 楊書瑋

Jeff Yang Effect of Polarization-Matched n-Type AlGaInN Electron-Blocking Layer on the Optoelectronic Properties of Blue InGaN Light-Emitting Diodes Yun Li, You Gao, Miao He, Jun Zhou, Yan Lei, Li Zhang, Kebao Zhu, and Yulong Chen 2

Outline Introduction Experiment Result and Discussion Conclusion 3

Introduction Conventional p-type electron- blocking layer (EBL) can be used a solution to reduce the electron leakage current. However, the p-type EBL also impeded the injection of holes into the active region. In this paper, we study the performances of blue InGaN LEDs by using a polarization-matched n-type AlGaInN (N-AlGaInN) EBL to replace p-AlGaInN EBL, p-AlGaInN EBL and n-AlGaN EBL in the active region. Conventional p-type electron- blocking layer (EBL) can be used a solution to reduce the electron leakage current. However, the p-type EBL also impeded the injection of holes into the active region. In this paper, we study the performances of blue InGaN LEDs by using a polarization-matched n-type AlGaInN (N-AlGaInN) EBL to replace p-AlGaInN EBL, p-AlGaInN EBL and n-AlGaN EBL in the active region. 4

Chip Size: 300*300 μm 2 Fig. 1. Schematic diagram of InGaN LED structures with P-AlGaInN, N-AlGaN and N-AlGaInN EBL. Chip Size: 300*300 μm 2 Fig. 1. Schematic diagram of InGaN LED structures with P-AlGaInN, N-AlGaN and N-AlGaInN EBL. Experiment Samplecomparing LEDIP-Al 0.38 Ga 0.46 In 0.16 N LEDIIN-Al 0.15 Ga 0.85 N LEDIIIN-Al 0.38 Ga 0.46 In 0.16 N Detail Buffer50nm-thick MQW5-pairs Barrier-10nm*6 Well-5nm*5 p-GaN250nm 5

Fig. 6. Band diagrams and quasi-Fermi levels of the LEDs with: (a) P-AlGaInN, (b) N-AlGaInN, and (c) N- AlGaN layers at 180 mA. Result and Discussion 6

Fig. 4. (a) Electron and (b) hole concentrations of the LEDs with P-AlGaInN, N-AlGaInN and P-AlGaN EBLs at 180 mA. 7

Conclusion The simulation results show that the N-AlGaInN EBL is a best candidate the concentration of electrons and holes within the active region of the LEDs with a N-AlGaInN EBL are more uniform, and the electron leakage current is also dramaticlly reduced. 8

Jeff Yang

Outline Introduction Experiment Result and Discussion Conclusion 10

Introduction Recently published studies point out that the electron confinement by a typical AlGaN EBL is not sufficiently effective to solve the efficiency droop problem. Furthermore, the use of AlGaN EBL can cause some undesired effects such as prohibiting the injection efficiency of holes into the active region. In this study, the characteristics of the nitride-based blue LED without an EBL are analyzed. We have discussed the advantages of the LED without an EBL, when compared with those of the similar LED with an AlGaN HBL. We have also investigated the optical and electrical properties of the LEDs with undoped or p- type doped GaN barriers when no EBL is used. 11

Experiment Chip Size: 300*300um NO.EBL / Thickness / ConcentrationMQW 4pairsBarrier variation AP-Al 0.15 Ga 0.85 N / 20nm / 7E17 GaN15nm / In 0.2 Ga 0.8 N2.2nm First Barrier (n-5E18) Last Barrier (p-7E17) u-Barrier B* C*p-Barrier (3E17) DN-Al 0.07 Ga 0.93 N / 20nm / 5E18P-Barrier (3E17) 12

Fig. 3. Energy band diagrams of u-GaN barrier LEDs (a) with an AlGaN EBL and (b) without an EBL at 150 mA. 13

Fig. 5. (a) Hole and (b) electron concentrations of the non-EBL p-GaN barrier LEDs with and without a HBL around the active region at 150 mA. 14

Fig. 6. (a) EL spectra at 150 mA and (b) IQE versus injection current for the LEDs of the four structures. 15

Conclusion The use of the p-type barriers can effectively suppress the spillover of electrons out of the active region, as well as increase the hole concentration. The insertion of the HBL can enhance the hole confinement. the efficiency droop of the new structure is markedly improved. 16

Reference Effect of electron blocking layer on efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes Sang-Heon Han, Dong-Yul Lee, Sang-Jun Lee, Chu-Young Cho, Min-Ki Kwon, S. P. Lee, D. Y. Noh, Dong- Joon Kim, Yong Chun Kim, and Seong-Ju Park Hole Injection and Electron Overflow Improvement in 365nm Light-Emitting Diodes by Band-Engineering Electron Blocking Layer Yi-Keng Fu1, Yu-Hsuan Lu2, Rong Xuan1;3, Jenn-Fang Chen3, and Yan-Kuin Su2 Advantages of Blue LEDs With Graded-Composition AlGaN/GaN Superlattice EBL Bing-Cheng Lin, Kuo-Ju Chen, Hau-Vei Han, Yu-Pin Lan, Ching-Hsueh Chiu, Chien-Chung Lin, Member, IEEE, Min-Hsiung Shih, Member, IEEE, Po-Tsung Lee, and Hao-Chung Kuo, Senior Member, IEEE 氣體分子極化率的量測 靜電場 電極化 17

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