在本篇論文中，我們以有機金屬化學氣相沉積法之技術成長以穿隧層串聯之氮化鎵系列光電元件，並研究涵蓋光電特性的相關性質。
為了克服發光二極體效率下降問題與改善其外部量子效率，首先，我們成長以穿隧層串聯主動區之氮化鎵系列多重量子井發光二極體。從X射線繞射頻譜發現，具穿隧層之發光二極體其磊晶品質幾乎與傳統發光二極體相同。與傳統發光二極體相比，我們發現具穿隧層之發光二極體可提升35%的光輸出功率由於重複使用電子和電洞促使更多光子的產生。當我們增加注入電流密度至80安培每平方厘米，我們發現具穿隧層之發光二極體與傳統發光二極體之外部量子效率下降比例分別為36.9%與35.0%。此外，我們發現注入電流密度為20安培每平方厘米時，具穿隧層之發光二極體有較高之順向偏壓為8.94伏特。從穿隧層之發光二極體觀察較高之順向偏壓應歸因於大的穿隧層阻值。
接下來，為實現高外部量子效率和更小效率下降，我們必須要降低穿隧層阻值。我們成長具混合型穿隧層串聯之氮化鎵系列發光二極體。與傳統發光二極體相比，我們發現具穿隧層之發光二極體與具混合型穿隧層之發光二極體分別可提升35%與80%光輸出功率。另外，具穿隧層之發光二極體與具混合型穿隧層之發光二極體其穿隧層阻值分別為6.05×10-3和1.95×10-3歐姆•平方厘米。同時還發現，使用混合型穿隧層可讓效率下降情形變小。這些改進可以全部歸於氮化鋁鎵/氮化銦鎵接面處累積較大的極化電荷可能提高的穿隧電流。此外，具混合型穿隧層串聯之氮化鎵系列發光二極體是高度可靠的。
接著，我們提出使用穿隧層結構以串聯綠色多重量子井主動區和藍色多重量子井主動區，並成長氮化鎵系列雙色發光二極體。結果發現，光輸出功率從穿隧層串聯之發光二極體是比那些從綠色傳統發光二極體和藍色傳統發光二極體觀察的總和僅略小。這表明大多數注入的載子可以通過的穿隧層和穿隧後可以重複用於光子的產生。此外，我們所提出的雙色發光二極體是高度可靠的。
接下來，我們延續使用穿隧層結構以串聯綠色多重量子井主動區和藍色多重量子井主動區，並進一步塗覆紅色螢光粉於綠/藍雙色具穿隧層串聯之發光二極體之上，製作出白光發光二極體。結果發現，“雙色具穿隧層串聯之發光二極體 + 紅色螢光粉”之CIE色彩座標位於（0.30，0.35），同時其色溫為4306絕對溫度和演色性指數為68。這說明，塗覆紅色螢光粉於綠/藍雙色具穿隧層串聯之發光二極體之上具有高潛力成為混成白光發光二極體的方式。
最後，我們說明具混合型穿隧層串聯雙區域之氮化鎵系列太陽能電池實作成果。從X射線繞射頻譜發現，具穿隧層之太陽能電池其磊晶品質幾乎與傳統太陽能電池相同。與單區域吸收之太陽能電池相比，我們發現運用混合型穿隧層串聯雙區域之太陽能電池可達到更高光電轉換效率。這些效能提升說明混合型穿隧層是有益於太陽能電池主動區之串聯。

In this dissertation, cascaded GaN-based optoelectronic devices with tunnel junction layers (TJLs) have been grown by metalorganic chemical vapor phase deposition (MOCVD) technique, and related characterizations including optical and electrical properties were also studied.
In order to overcome the efficiency droop problem and and improve externl quantum efficiency of light emitting diodes (LEDs), firstly, we fabricated GaN-based multiquantum well LED with tunnel junction (TJ)-cascaded active region. It was found from x-ray diffraction (XRD) spectra that crystal quality of the TJ LED was almost identical to that of the conventional LED. Compared with the conventional LED, it was found that we could achieve 35% higher light output power from the TJ LED due to the repeated use of electron and holes for photon generation. It was also found that external quantum efficiency (EQE) drooped by 36.9% and 35.0% for the TJ LED and the conventional LED, respectively, as we increased the injection current density to 80 A/cm2. Furthermore, it was found that forward voltages measured with an injection current density of 20 A/cm2 were 8.94 V for the TJ LED. The large forward voltage observed from the TJ LED should be attributed to the large TJ resistance.
Secondly, to achieve high EQE and smaller drooping, we must need to reduce the TJ resistance. We fabricated the cascaded GaN LEDs with hybrid TJL. Compared with the conventional LED, it was found that we could enhance the light output power by 35% and 80% from the LED with TJL and the LED with hybrid TJL. It was also found that the TJ resistances were 6.05×10-3 and 1.95×10-3 Ω·cm2 for the LED with TJL and the LED with hybrid TJL, respectively. It was also found that the use of hybrid TJL could result in smaller efficiency droop. These improvements could all be attributed to the larger polarization charges induced at the AlGaN/InGaN interface which could enhance the tunneling current. Furthermore, it was found that the cascaded GaN LEDs with hybrid TJL were also reliable.
Thirdly, we propose the use of TJ structure to cascade a green multiquantum well (MQW) active region and a blue MQW active region, and the fabrication of GaN-based dual-color LEDs. It was found that light output power observed from the TJ cascaded LED was only slightly smaller than the summation of those observed from the green LED and the blue LED. This suggests that most of the injected carriers could tunnel through the TJ and could be repeatedly used for photon generation. Furthermore, it was found that the proposed dual-color LEDs was highly reliable.
Fourth, we propose the use of tunnel junction (TJ) structure to cascade a green multiquantum well (MQW) active region and a blue MQW active region, and the fabrication of white-light LED by using green/blue dual-color TJ LEDs coated with red phosphors. It was found that the CIE color coordinates of “dual-color TJ LED + red phosphor” locates at (0.30, 0.35) with the color temperature, TC=4306 K and color-rendering index, CRI =68. This suggests that green/blue dual-color TJ LEDs coated with red phosphors has high potential to become a way of the white LED.
Finnaly, we report the fabrication of cascaded GaN-based dual-region solar cells (SCs) with hybrid TJL. Compared with the conventional SCs, it was found from XRD spectra that crystal quality of the TJ SCs was almost identical to that of the conventional SCs. Compared with the single region SCs, it was found that the use of dual region SCs with hybrid TJL could result in higher conversion efficiency. The improvements show that hybrid TJL was useful to connect multiple active regions in series in solar cells.

Chapter 1
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[20] F. Akyol, S. Krishnamoorthy and S. Rajan, “Tunneling-based carrier regeneration in cascaded GaN light emitting diodes to overcome efficiency droop,” Appl. Phys. Lett., vol. 103, Art. 081107 (2013).
[21] J. Piprek, “Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel junction-cascaded active regions”, Appl. Phys. Lett., vol. 1.4, Art. 051118 (2014).
[22] M. C. Tsai, B. Leung, T. C. Hsu and Y. K. Kuo, “Tandem structure for efficiency improvement in GaN based light-emitting diodes”, IEEE/OSA J. Lightwave Technol., vol. 32, pp. 1801-1806 (2014).
[23] I. Ozden, E. Makarona, A. V. Nurmikko, T. Takeuchi and M. Krames, “A dual-wavelength indium gallium nitride quantum well light emitting diode”, Appl. Phys. Lett., vol. 79, pp. 2532-2534 (2001).
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Chapter 2
[1] S. Nakamura, M. Senoh, S. I. Nagahama, N. Iwasa, T. Yamada, T. Matsushita, H. Kiyoku and Y. Sugimoto, “InGaN-Based Multi-Quantum-Well-Structure Laser Diodes,” Jpn. J. Appl. Phys., vol. 35, pp. L74–L76 (1997).
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[5] S. Nakamura, M. Senoh, N. Iwasa and S.I. Nagahama, “High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures,” Jpn. J. Appl. Phys., vol. 34, pp. L797–L799 (1995).
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Chapter 3
[1] S. Nakamura, M. Senoh, N. Iwasa and S. Nagahama, “High-power InGaN single-quantum-well-structure blue and violet light-emitting diodes,” Appl. Phys. Lett., vol. 67, pp. 1868–1870 (1995).
[2] E. F. Schubert and J. K. Kim, “Solid-state light sources getting smart,” Science, vol. 308, pp. 1274-1278 (2005).
[3] X. A. Cao, Y. Yang and H. Guo, “On the origin of efficiency roll-off in InGaN-based light-emitting diodes”, J. Appl. Phys., vol. 104, Art. 093108 (2008).
[4] A. David, M. J. Grundmann, J. F. Kaeding, N. F. Gardner, T. G. Mihopoulos and M. R. Krames, “Carrier distribution in (0001) InGaN/GaN multiple quantum well light-emitting diodes”, Appl. Phys. Lett., vol. 92, Art. 053502 (2008).
[5] N. F. Gardner, G. O. Mueller, Y. C. Shen, G. Chen, S. Watanabe, W. Gotz and M. R. Krames, “Blue-emitting InGaN-GaN double-heterostructure light-emitting diodes reaching maximum quantum efficiency above 200 A/cm2”, Appl. Phys. Lett., vol. 91, Art. 243506 (2007).
[6] Y. Y. Lin, R. W. Chuang, S. J. Chang, S. G. Li, Z. Y. Jiao, T. K. Ko and C. H. Liu, "GaN-based LEDs with a chirped multiquantum barrier structure", IEEE Photon. Technol. Lett., vol. 24, pp. 1600-1602 (2012).
[7] G. Y. Liu, J. Zhang, C. K. Tan and N. Tansu, “Efficiency-droop suppression by using large-bandgap AlGaInN thin barrier layers in InGaN quantum-well light-emitting diodes”, IEEE Photon. J., vol. 5, Art. 2201011 (2013).
[8] C. H. Chiu, D. W. Lin, C. C. Lin, Z. Y. Li, W. T. Chang, H. W. Hsu, H. C. Kuo, T. C. Lu, S. C. Wang, W. T. Liao, T. Tanikawa, Y. Honda, M. Yamaguchi and N. Sawaki, “Reduction of efficiency droop in semipolar (1101) InGaN/GaN light emitting diodes grown on patterned silicon substrates”, Appl. Phys. Express, vol. 4, Art. 012105 (2011).
[9] I. Ozden, E. Makarona, A. V. Nurmikko, T. Takeuchi and M. Krames, “A dual-wavelength indium gallium nitride quantum well light emitting diode”, Appl. Phys. Lett., vol. 79, pp. 2532–2534 (2001).
[10] C. H. Chen, S. J. Chang, Y. K. Su, J. K. Sheu, J. F. Chen, C. H. Kuo and Y. C. Lin, “Nitride-based cascade near white light-emitting diodes,” IEEE Photonics Technol. Lett., vol. 14, pp. 908-910 (2002).
[11] T. Takeuchi, G. Hasnain, S. Corzine, M. Hueschen, R. P. Schneider, Jr., C. Kocot, M. Blomqvist, Y. L. Chang, D. Lefforge, M. R. Krames, L. W. Cook and S. A. Stockman, “GaN-based light emitting diodes with tunnel junctions,” Jpn. J. Appl. Phys., vol. 40, pp. L861-863 (2001).
[12] M. Kaga, T. Morita, Y. Kuwano, K. Yamashita, K. Yagi, M. Iwaya, T. Takeuchi, S. Kamiyama and I. Akasaki, “GaInN-based tunnel junctions in n–p–n light emitting diodes,” Jpn. J. Appl. Phys., vol. 52, Art. 08JH06 (2013).
[13] F. Akyol, S. Krishnamoorthy and S. Rajan, “Tunneling-based carrier regeneration in cascaded GaN light emitting diodes to overcome efficiency droop,” Appl. Phys. Lett., vol. 103, Art. 081107 (2013).
[14] J. Piprek, “Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel junction-cascaded active regions”, Appl. Phys. Lett., vol. 1.4, Art. 051118 (2014).
[15] M. C. Tsai, B. Leung, T. C. Hsu and Y. K. Kuo, “Tandem structure for efficiency improvement in GaN based light-emitting diodes”, IEEE/OSA J. Lightwave Technol., vol. 32, pp. 1801-1806 (2014).
[16] Z. H. Zhang, S. T. Tan, Z. Kyaw, Y. Ji, W. Liu, Z. Ju, N. Hasanov, X. W. Sun and H. V. Demir, “InGaN/GaN light-emitting diode with a polarization tunnel junction,” App. Phys. Lett., vol. 102, Art. 193508 (2013).
[17] J. Piprek, “Blue light emitting diode exceeding 100% quantum efficiency”, Phys. Status Solidi RRL, vol. 8, pp. 424-426 (2014).
[18] S. Chichibu, T. Azuhata and T. Sota and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures”, Appl. Phys. Lett., vol. 92, pp. 4188-4190 (1996).

Chpater 4
[1] S. Nakamura, M. Senoh, N. Iwasa and S. Nagahama, “High-power InGaN single-quantum-well-structure blue and violet light-emitting diodes,” Appl. Phys. Lett., vol. 67, pp. 1868-1870 (1995).
[2] C. T. Lee, U. Z. Yang, C. S. Lee and P. S. Chen, “White light emission of monolithic carbon-implanted InGaN–GaN light-emitting diodes,” IEEE Photon. Technol. Lett., vol. 18, pp. 2029-2031 (2006).
[3] L. W. Wu, S. J. Chang, Y. K. Su, R. W. Chuang, Y. P. Hsu, C. H. Kuo, W. C. Lai, T. C. Wen, J. M. Tsai and J. K. Sheu, "In0.23Ga0.77N/GaN MQW LEDs with a low temperature GaN cap layer", Solid State Electron., vol. 47, pp. 2027-2030 (2003).
[4] I. Ozden, E. Makarona, A. V. Nurmikko, T. Takeuchi and M. Krames, “A dual-wavelength indium gallium nitride quantum well light emitting diode”, Appl. Phys. Lett., vol. 79, pp. 2532-2534 (2001).
[5] C. H. Chen, S. J. Chang, Y. K. Su, J. K. Sheu, J. F. Chen, C. H. Kuo and Y. C. Lin, “Nitride-based cascade near white light-emitting diodes,” IEEE Photonics Technol. Lett., vol. 14, pp. 908-910 (2002).
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[7] C. L. Chao, R. Xuan, H. H. Yen, C. H. Chiu, Y. H. Fang, Z. Y. Li, B. C. Chen, C. C. Lin, C. H. Chiu, Y. D. Guo, H. C. Kuo, J. F. Chen, and S. J. Cheng, “Reduction of efficiency droop in InGaN light-emitting diode grown on self-separated freestanding GaN substrates,” IEEE Photonics Technol. Lett., vol. 23, pp. 798-800 (2011).
[8] APSYS, Crosslight Software Inc., Burnaby, Canada.
[9] J. Piprek, “Origin of InGaN/GaN light-emitting diode efficiency improvements using tunnel junction-cascaded active regions”, Appl. Phys. Lett., vol. 14, Art. 051118 (2014).
[10] S. J. Chang, W. H. Lin and C. T. Yu, “GaN-based multiquantum well light-emitting diodes with tunnel-junction-cascaded active regions”, IEEE Electron Dev. Lett., vol. 36, pp. 366-368 (2015).
[11] M. C. Tsai, B. Leung, T. C. Hsu, and Y. K. Kuo, “Low Resistivity GaN-based polarization-induced tunnel junctions”, IEEE/OSA J. Lightwave Technol., vol. 31, pp. 3575-3581 (2013).
[12] S. J. Chang, N. M. Lin and S. C. Shei, "GaN-based power flip-chip LEDs with SILAR and hydrothermal ZnO nanorods", IEEE J. Sel. Top. Quan. Electron., vol. 21, Art. 9100405 (2015).
[13] S. J. Chang, L. Lu, Y. Y. Lin and S. G. Li, "GaN-based light-emitting diodes with strain compensation buffer layer", IEEE/OSA J. Display Technol., vol. 9, pp. 910-914 (2013).
[14] Y. Y. Zhang and Y. A. Yin, “Tunneling-based carrier regeneration in cascaded GaN light emitting diodes to overcome efficiency droop,” Appl. Phys. Lett., vol. 99, Art. 221103 (2011).
[15] S. J. Chang, C. S. Chang, Y. K. Su, R. W. Chuang, Y. C. Lin, S. C. Shei, H. M. Lo, H. Y. Lin and J. C. Ke, "Highly reliable nitride based LEDs with SPS+ITO upper contacts", IEEE J. Quan. Electron., vol. 39, pp. 1439-1443 (2003).
[16] J. Piprek, “Blue light emitting diode exceeding 100% quantum efficiency”, Phys. Status Solidi RRL, vol. 8, pp. 424-426 (2014).
[17] S. Chichibu, T. Azuhata and T. Sota and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures”, Appl. Phys. Lett., vol. 92, pp. 4188-4190 (1996).

Chapter 5
[1] S. Nakamura, M. Senoh, N. Iwasa, and S. Nagahama, “High-power InGaN single-quantum-well-structure blue and violet light-emitting diodes,” Appl. Phys. Lett., vol. 67, pp. 1868-1870 (1995).
[2] C. T. Lee, U. Z. Yang, C. S. Lee, and P. S. Chen, “White light emission of monolithic carbon-implanted InGaN–GaN light-emitting diodes,” IEEE Photon. Technol. Lett., vol. 18, pp. 2029-2031 (2006).
[3] L. W. Wu, S. J. Chang, Y. K. Su, R. W. Chuang, Y. P. Hsu, C. H. Kuo, W. C. Lai, T. C. Wen, J. M. Tsai, and J. K. Sheu, "In0.23Ga0.77N/GaN MQW LEDs with a low temperature GaN cap layer", Solid-State Electron., vol. 47, pp. 2027-2030 (2003).
[4] I. Ozden, E. Makarona, A. V. Nurmikko, T. Takeuchi, and M. Krames, “A dual-wavelength indium gallium nitride quantum well light emitting diode”, Appl. Phys. Lett., vol. 79, pp. 2532-2534 (2001).
[5] C. H. Chen, S. J. Chang, Y. K. Su, J. K. Sheu, J. F. Chen, C. H. Kuo, and Y. C. Lin, “Nitride-based cascade near white light-emitting diodes,” IEEE Photon. Technol. Lett., vol. 14, pp. 908-910 (2002).
[6] H. Zhang, E. J. Miller, and E. T. Yu, “Measurement of polarization charge and conduction-band offset at InxGa1-xN/GaN heterojunction interfaces”, Appl. Phys. Lett., vol. 84, pp. 4644-4646 (2004).
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[9] S. Krishnamoorthy, F. Akyol, P. S. Park, and S. Rajan, “Low resistance GaN/InGaN/GaN tunnel junctions”, Appl. Phys. Lett., vol. 102, Art. 113503 (2013).
[10] S. J. Chang, W. H. Lin, and C. T. Yu, “GaN-based multiquantum well light-emitting diodes with tunnel-junction-cascaded active regions”, IEEE Electron Dev. Lett., vol. 36, pp. 366-368 (2015).
[11] M. C. Tsai, B. Leung, T. C. Hsu, and Y. K. Kuo, “Low Resistivity GaN-based polarization-induced tunnel junctions”, IEEE/OSA J. Lightwave Technol., vol. 31, pp. 3575-3581 (2013).
[12] APSYS User’s Manual. Crosslight Software Inc., Vancouver, BC, Canada. [Online]. Available: http://www.crosslight.com.
[13] S. J. Chang, W. H. Lin, and W. S. Chen, “Cascaded GaN light-emitting diodes with hybrid tunnel junction layers”, IEEE J. Quan. Electron., vol. 51, Art. 3300505 (2015).
[14] M. R. Krames, O. B. Shchekin, R.Mueller-Mach, G. O.Mueller, L. Zhou, G. Harbers, and M. G. Craford, “Status and future of high-power light emitting diodes for solid-state lighting,” IEEE/OSA J. Disp. Technol., vol. 3, pp. 160–175 (2007).
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[16] S. J. Chang, N. M. Lin, and S. C. Shei, "GaN-based power flip-chip LEDs with SILAR and hydrothermal ZnO nanorods", IEEE J. Sel. Top. Quan. Electron., vol. 21, Art. 9100405 (2015).
[17] C. F. Shen, S. J. Chang, W. S. Chen, T. K. Ko, C. T. Kuo, and S. C. Shei, “Nitride-based high-power flip-chip LED with double-side patterned sapphire substrate”, IEEE Photon. Technol. Lett., vol. 19, pp. 780-782 (2007).
[18] Y. Y. Zhang and Y. A. Yin, “Performance enhancement of blue light-emitting diodes with a special designed AlGaN/GaN superlattice electron-blocking layer,” Appl. Phys. Lett., vol. 99, Art. 221103 (2011).
[19] S. J. Chang et al., “Highly reliable nitride-based LEDs with SPS+ITO upper contacts,” IEEE J. Quan. Electron., vol. 39, pp. 1439–1443 (2003).
[20] J. Piprek, “Blue light emitting diode exceeding 100% quantum efficiency,” Phys. Status Solidi-Rapid Res. Lett., vol. 8, no. 5, pp. 424–426 (2014).
[21] S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures”, Appl. Phys. Lett., vol. 92, pp. 4188-4190 (1996).
[22] M. F. Schubert, S. Chajed, J. K. Kim, E. F. Schubert, D. D. Koleske, M. H. Crawford, S. R. Lee, A. J. Fischer, G. Thaler, and M. A. Banas, “Effect of dislocation density on efficiency droop in GaInN/GaN light-emitting diodes,” Appl. Phys. Lett., vol. 91, pp. 23114-1–23114-3 (2007).

Chapter 6
S. Nakamura, M. Senoh, N. Iwasa, and S. Nagahama, “High-power InGaN single-quantum-well-structure blue and violet light-emitting diodes,” Appl. Phys. Lett., vol. 67, pp. 1868-1870 (1995).
[2] C. T. Lee, U. Z. Yang, C. S. Lee, and P. S. Chen, “White light emission of monolithic carbon-implanted InGaN–GaN light-emitting diodes,” IEEE Photon. Technol. Lett., vol. 18, pp. 2029-2031 (2006).
[3] L. W. Wu, S. J. Chang, Y. K. Su, R. W. Chuang, Y. P. Hsu, C. H. Kuo, W. C. Lai, T. C. Wen, J. M. Tsai, and J. K. Sheu, "In0.23Ga0.77N/GaN MQW LEDs with a low temperature GaN cap layer", Solid-State Electron., vol. 47, pp. 2027-2030 (2003).
[4] M. Yamada, Y. Narukawa, and T. Mukai, “Phosphor free high-luminous- efficiency white light-emitting diodes composed of InGaN multiquantum well,” Jpn. J. Appl. Phys., vol. 41, no. 3A, pp. L246–L248, Mar. (2002).
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[8] M. R. Krames, O. B. Shchekin, R. Mueller-Mach, G. O.Mueller, L. Zhou, G. Harbers, and M. G. Craford, “Status and future of high-power light emitting diodes for solid-state lighting,” IEEE/OSA J. Disp. Technol., vol. 3, pp. 160–175 (2007).
[9] Y.-H. Won, H.S. Jang, W.B. Im, D.Y. Jeon, J.S. Lee, Tunable full-color- emitting La0.827Al11.9O19.09: Eu2+, Mn2+ phosphor for application to warm white-light-emitting diodes. Appl. Phys. Lett., vol. 89, Art. 231909 (2006).
[10] I. Ozden, E. Makarona, A. V. Nurmikko, T. Takeuchi, and M. Krames, “A dual-wavelength indium gallium nitride quantum well light emitting diode”, Appl. Phys. Lett., vol. 79, pp. 2532-2534 (2001).
[11] C. H. Chen, S. J. Chang, Y. K. Su, J. K. Sheu, J. F. Chen, C. H. Kuo, and Y. C. Lin, “Nitride-based cascade near white light-emitting diodes,” IEEE Photon. Technol. Lett., vol. 14, pp. 908-910 (2002).
[12] S. Krishnamoorthy, F. Akyol, P. S. Park, and S. Rajan, “Low resistance GaN/InGaN/GaN tunnel junctions”, Appl. Phys. Lett., vol. 102, Art. 113503 (2013).
[13] S. J. Chang, W. H. Lin, and C. T. Yu, “GaN-based multiquantum well light-emitting diodes with tunnel-junction-cascaded active regions”, IEEE Electron Dev. Lett., vol. 36, pp. 366-368 (2015).
[14] M. C. Tsai, B. Leung, T. C. Hsu, and Y. K. Kuo, “Low Resistivity GaN-based polarization-induced tunnel junctions”, IEEE/OSA J. Lightwave Technol., vol. 31, pp. 3575-3581 (2013).
[15] APSYS User’s Manual. Crosslight Software Inc., Vancouver, BC, Canada. [Online]. Available: http://www.crosslight.com.
[16] S. J. Chang, W. H. Lin, and W. S. Chen, “Cascaded GaN light-emitting diodes with hybrid tunnel junction layers”, IEEE J. Quan. Electron., vol. 51, Art. 3300505 (2015).
[17] S. J. Chang, N. M. Lin, and S. C. Shei, "GaN-based power flip-chip LEDs with SILAR and hydrothermal ZnO nanorods", IEEE J. Sel. Top. Quan. Electron., vol. 21, Art. 9100405 (2015).
[18] C. F. Shen, S. J. Chang, W. S. Chen, T. K. Ko, C. T. Kuo, and S. C. Shei, “Nitride-based high-power flip-chip LED with double-side patterned sapphire substrate”, IEEE Photon. Technol. Lett., vol. 19, pp. 780-782 (2007).
[19] Y. Y. Zhang and Y. A. Yin, “Performance enhancement of blue light-emitting diodes with a special designed AlGaN/GaN superlattice electron-blocking layer,” Appl. Phys. Lett., vol. 99, Art. 221103 (2011).
[20] S. J. Chang et al., “Highly reliable nitride-based LEDs with SPS+ITO upper contacts,” IEEE J. Quan. Electron., vol. 39, pp. 1439–1443 (2003).
[21] S. Chichibu, T. Azuhata, T. Sota, and S. Nakamura, “Spontaneous emission of localized excitons in InGaN single and multiquantum well structures”, Appl. Phys. Lett., vol. 92, pp. 4188-4190 (1996).
[22] W. H. Lin, S. J. Chang, and W. S. Chen, “GaN-based Dual-Color Light-Emitting Diodes with a Hybrid Tunnel Junction Structure,” IEEE J. Disp. Technol., vol. XX, pp. XX–XX (2015).

Chapter 7
B.U. Ye, B.J. Kim, Y.H. Song, J.H. Son, H.K. Yu, M.H. Kim, J.L. Lee, J.M. Baik, “Enhancing Light Emission of Nanostructured Vertical Light‐Emitting Diodes by Minimizing Total Internal Reflection,” Adv. Funct. Mater., vol. 22, pp. 632–639 (2012).
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