n LightEmitting Diodes LED n Laser Diodes VCSEL

近年來主要的研究主題 n Light-Emitting Diodes (LED) n Laser Diodes & VCSEL n Light-Emitting Diodes (OLED) n Solar Cells (Si & III-V) n Others (III-N Band Structures & Bowing Parameters, Solid-State Lasers, etc. ) (數篇SCI論文被引用 數在 10次以上) 17

APSYS模擬軟體 (Advanced Physical Models of Semiconductor Devices) n LED、OLED、與Solar Cell等光電半導體 元件的設計、模擬、與分析，均可以借助 APSYS模擬軟體來執行。 n APSYS可以經由解Poisson’s equation、 current continuity equation、carrier energy transport equation、以及quantum mechanical wave equation等方程式，求得 光電半導體元件的各種光學與電子特性。 n APSYS亦使用Ray-Tracing技術，分析由元 件所輸出之光強度以及光場隨角度之分佈 情形。 19

Examples of Simulations n. Simulation of LEDs n. Simulation of Laser Diodes n. Simulation of VCSELs n. Simulation of OLEDs n. Simulation of Solar Cells 21

Simulation of LEDs 22

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n After comparing, preferable designs of the staggered QWs are In 0. 20 Ga 0. 80 N (1. 4 nm)–In 0. 26 Ga 0. 74 N (1. 6 nm), In 0. 21 Ga 0. 79 N (1. 4 nm)–In 0. 25 Ga 0. 75 N (1. 6 nm), and In 0. 22 Ga 0. 78 N (1. 5 nm)– In 0. 24 Ga 0. 76 N (1. 5 nm), which are named as structure A, structure B, and structure C, respectively. 24

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The effective potential height for holes in the valence band of the In. Ga. N/Al. Ga. N structure is lower than that of the In. Ga. N/Ga. N one (i. e. , 0. 255 e. V vs. 0. 282 e. V) owing to the slighter polarization effect in the last-barrier/EBL interface. n The effective potential height for the electrons in the conduction band of the In. Ga. N/Al. Ga. N structure becomes higher than the other structure (i. e. , 0. 367 e. V vs. 0. 355 e. V), which denotes the enhancement of electron confinement. 28 n

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The light performance of the blue In. Ga. N LEDs emitting in a spectral range from 435 to 445 nm can be enhanced effectively when the conventional Ga. N barrier layers are replaced by the low-indium-content In 0. 02 Ga 0. 98 N and In 0. 05 Ga 0. 95 N barrier layers. n The light performance of the 445 -nm LEDs with the In 0. 05 Ga 0. 95 N barrier layers is improved due to the increased overlap of electrons and holes inside the QW close to the p-side layers, which is the major source for radiative recombination. n 32

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n The strong electric field caused by the piezoelectric polarization charges at the interface between the P-Al. Ga. N and barrier layer lowers the conduction band energy in the last barrier. Our calculation shows that the percentages n of electron leakage current for the LEDs with P-Al. Ga. N and N-Al. Ga. N are 46. 1% and 4. 5%, respectively, at 120 m. A. Besides the relatively uniform distribution of holes in the QWs, the sufficiently reduced electron leakage current is also a major cause for the improvement in efficiency droop. 36

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Simulation of Laser Diodes 38

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Simulation of VCSELs 41

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Simulation of OLEDs 45

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Simulation of Solar Cells 48

太陽能電池的模擬與分析 n Investigation of current matching for In 0. 49 Ga 0. 51 P/Ga. As/Ge triple-juction tandem solar cell Band diagram Schematic drawing of the solar cell structure 49

上中下三個Cells的I-V曲線 Device current is limited by the smallest current. 50

中間Cell的最佳厚度 … 3. 8 µm … … Ø Change thickness of middle cell base layer. 0. 17 µm … Ø Change thickness of middle cell emitter layer when the base layer thickness is fixed at 3. 8 µm. 51

上中兩個Cells的電流匹配 Sun light power 0. 236 µm Sun light power at top cell decay Sun light power n Base layer thicknesses of middle at middle cell → 3. 8 μm n Emitter layer thicknesses of middle cell → 0. 17 μm n. Base layer thickness of top cell → 0. 236 μm 52

優化後的結構 n Schematic drawing of optimized structure The photon current density of the device can be improved by enhancing the middle cell photon current density. 53

太陽能電池模擬與分析的結論 The short-circuit current density is improved due to the achievement of current match. n The short-circuit current density is improved from 16. 56 to 18. 78 m. A/cm 2 and the conversion efficiency is increased by about 3%. n improved about 3% 54

Recent publication (I) Yen-Kuang Kuo, Jih-Yuan Chang, and Miao-Chan Tsai, “Enhancement in hole injection efficiency of blue In. Ga. N light-emitting diodes from reduced polarization by some specific designs on electron blocking layer”, Optics Letters, Accepted 4 September 2010. (SCI) [2008 Impact Factor = 3. 772, Ranked 4/64 in Optics] n Chih-Teng Liao, Miao-Chan Tsai, Bo-Ting Liou, Sheng-Horng Yen, and Yen -Kuang Kuo, “Improvement in output power of a 460 -nm In. Ga. N lightemitting diode using staggered quantum well”, Journal of Applied Physics, Accepted 8 July 2010. (SCI) [2008 Impact Factor = 2. 201, Ranked 20/95 in Physics, Applied Physics] n Yen-Kuang Kuo, Syuan-Huei Horng, Miao-Chan Tsai, Sheng-Horng Yen, and Shu-Hsuan Chang, “Effect of normal and reversed polarizations on optical characteristics of ultraviolet-violet In. Ga. N laser diodes”, Optics Communications, Vol. 283, Issue 19, pp. 3698– 3702, 1 October 2010. (SCI) [2008 Impact Factor = 1. 552, Ranked 23/64 in Optics] n Jih-Yuan Chang, Miao-Chan Tsai, and Yen-Kuang Kuo, “Advantages of blue In. Ga. N light-emitting diodes with Al. Ga. N barriers”, Optics Letters, Vol. 35, No. 9, pp. 1368– 1370, 1 May 2010. (SCI) [2008 Impact Factor = 3. 772, Ranked 4/64 in Optics] 55 n

Recent publication (II) Yen-Kuang Kuo, Miao-Chan Tsai, Sheng-Horng Yen, Ta-Cheng Hsu, and Yu. Jiun Shen, “Effect of p-type last barrier on efficiency droop of blue In. Ga. N lightemitting diodes”, IEEE Journal of Quantum Electronics, Vol. 46, No. 8, pp. 1214 – 1220, August 2010. (SCI) [2008 Impact Factor = 2. 413, Ranked 37/229 in Engineering, Electrical & Electronic] n Miao-Chan Tsai, Sheng-Horng Yen, and Yen-Kuang Kuo, “Carrier transportation and internal quantum efficiency of blue In. Ga. N light-emitting diodes with p-doped barriers”, IEEE Photonics Technology Letters, Vol. 22, No. 6, pp. 374– 376, 15 March 2010. (SCI) [2008 Impact Factor = 2. 173, Ranked 12/64 in Optics] n Jun-Rong Chen, Yung-Chi Wu, Shih-Chun Ling, Tsung-Shine Ko, Tien-Chang Lu, Hao-Chung Kuo, Yen-Kuang Kuo, and Shing-Chung Wang, “Investigation of wavelength-dependent efficiency droop in In. Ga. N light-emitting diodes”, Applied Physics B: Lasers and Optics, Vol. 98, No. 4, pp. 779– 789, March 2010. (SCI) [2008 Impact Factor = 2. 167, Ranked 13/64 in Optics] n Yen-Kuang Kuo, Syuan-Huei Horng, Sheng-Horng Yen, Miao-Chan Tsai, and Man-Fang Huang, Published online 26 November 2009, “Effect of polarization state on optical properties of blue-violet In. Ga. N light-emitting diodes”, Applied Physics A: Materials Science & Processing, Vol. 98, No. 3, pp. 509– 515, 4 January 2010. (SCI) [2008 Impact Factor = 1. 884, Ranked 30/95 in Physics, Applied Physics] 56 n

Recent publication (III) n n n Yen-Kuang Kuo, Jih-Yuan Chang, and Mei-Ling Chen, “Role of electron blocking layer in III-nitride laser diodes and light-emitting diodes”, Proceedings of SPIE, Vol. 7597, pp. 759720 -1– 759720 -9, Published online 25 February 2010. (EI) Shu-Hsuan Chang, Miao-Chan Tsai, Sheng-Horng Yen, Shu-Jeng Chang, and Yen-Kuang Kuo, “Numerical simulation on high-efficiency Ga. In. P/Ga. As/In. Ga. As triple-junction solar cells”, Proceedings of SPIE, Vol. 7597, pp. 759721 -1– 75972112, Published online 25 February 2010. (EI) 陳俊榮、張誌原、郭艷光、盧廷昌、郭浩中、王興宗, “高亮度氮化鎵發光二極體： 高驅動電流下的屏障”, 電子月刊, 第 16卷, 第 6期, 第 118至 129頁, 2010年 6月. Yen-Kuang Kuo, Jih-Yuan Chang, Miao-Chan Tsai, and Sheng-Horng Yen, “Advantages of blue In. Ga. N multiple-quantum well light-emitting diodes with In. Ga. N barriers”, Applied Physics Letters, Vol. 95, No. 1, pp. 011116 -1 - 011116 -3, Published online 10 July 2009. (SCI) [2008 Impact Factor = 3. 726, Ranked 10/95 in Physics, Applied Physics] Yen-Kuang Kuo, Miao-Chan Tsai, Sheng-Horng Yen, Ta-Cheng Hsu, and Yu. Jiun Shen, “Enhancement of light power for blue In. Ga. N light-emitting diodes by using low-indium-content In. Ga. N barriers”, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 15, No. 4, pp. 1115 -1121, 5 August 2009. (SCI) [2008 Impact Factor = 2. 518, Ranked 9/64 in Optics] 57

Recent publication (IV) Yen-Kuang Kuo, Miao-Chan Tsai, and Sheng-Horng Yen, “Numerical simulation of blue In. Ga. N light-emitting diodes with polarization-matched Al. Ga. In. N electron-blocking layer and barrier layer”, Optics Communications, Vol. 282, Issue 21, pp. 4252 -4255, 1 November 2009. (SCI) [2008 Impact Factor = 1. 552, Ranked 23/64 in Optics] n Sheng-Horng Yen, Miao-Chan Tsai, Meng-Lun Tsai, Yu-Jiun Shen, Ta-Cheng Hsu, and Yen-Kuang Kuo, “Effect of n-type Al. Ga. N layer on carrier transportation and efficiency droop of blue In. Ga. N light-emitting diodes”, IEEE Photonics Technology Letters, Vol. 21, No. 14, pp. 975 -977, 15 July 2009. (SCI) [2008 Impact Factor = 2. 173, Ranked 12/64 in Optics] n Sheng-Horng Yen, Miao-Chan Tsai, Meng-Lun Tsai, Yu-Jiun Shen, Ta-Cheng Hsu, and Yen-Kuang Kuo, Published online 26 June 2009, “Theoretical investigation of Auger recombination on internal quantum efficiency of blue light-emitting diodes”, Applied Physics A: Materials Science & Processing, Vol. 97, Issue 3, pp. 705 -708, 4 November 2009. (SCI) [2008 Impact Factor = 1. 884, Ranked 30/95 in Physics, Applied Physics] n Miao-Chan Tsai, Sheng-Horng Yen, Shu-Hsuan Chang, and Yen-Kuang Kuo, “Effect of spontaneous and piezoelectric polarization on optical characteristics of ultraviolet Al. Ga. In. N light-emitting diodes”, Optics Communications, Vol. 282, Issue 8, pp. 1589 -1592, 15 April 2009. (SCI) [2008 Impact Factor = 1. 552, Ranked 23/64 in Optics] 58 n

Recent publication (V) Jun-Rong Chen, Yung-Chi Wu, Tien-Chang Lu, Hao-Chung Kuo, Yen-Kuang Kuo, and Shing-Chung Wang, “Numerical study on lateral mode behavior of 660 -nm In. Ga. P/Al. Ga. In. P multiple-quantum-well laser diodes”, Optical Review, Vol. 16, No. 3, pp. 375– 382, Published online 9 June 2009. (SCI) [2008 Impact Factor = 0. 545, Ranked 51/64 in Optics] n Yen-Kuang Kuo, Ying-Chung Lu, Miao-Chan Tsai, and Sheng-Horng Yen, “Numerical simulation of 405 -nm In. Ga. N laser diodes with polarizationmatched Al. Ga. In. N electron-blocking layer and barrier layer”, Proceedings of SPIE, Vol. 7211, 72111 B-1 – 72111 B-8, January 2009. (EI) n Bo-Ting Liou, Miao-Chan Tsai, Chih-Teng Liao, Sheng-Horng Yen, and Yen. Kuang Kuo, “Numerical investigation of blue In. Ga. N light-emitting diodes with staggered quantum wells”, Proceedings of SPIE, Vol. 7211, pp. 72111 D-1 – 72111 D-8, January 2009. (EI) n Shu-Hsuan Chang, Chien-Yang Wen, Yi-Hsiang Huang, and Yen-Kuang Kuo, “Numerical simulation on white OLEDs with dotted-line doped emitting layers”, Proceedings of SPIE, Vol. 7213, 72131 J-1 – 72131 J-8, January 2009. (EI) n 59

Blue Laser Laboratory Thank you for your attention. 60