臺灣博碩士論文加值系統

　　本論文主要針對具有光子循環結構之氮化銦鎵/氮化鎵發光二極體其光電特性作相關探討。光子循環結構發光二極體(photon-recycling structure light-emitting diodes，PRSLEDs)元件透過於傳統電激發近紫外光垂直式結構發光二極體(vertical light-emitting diodes，VLEDs)元件上增加藍/綠光轉換層(converter)多重量子井(multiple quantum well，MQW)結構，使部分電激發近紫外光光子受轉換層吸收後輻射複合釋放出光激發藍/綠光，與傳統電激發藍/綠光二極體之發光機制有所差異。

　　光子循環結構發光二極體之設計相較於傳統電激發垂直式結構發光二極體而言，元件電特性明顯獲得改善。401nm近子外光波段之垂直式結構發光二極體於增加30對(pairs)綠光轉換層量子井結構之後，串聯電阻(series rsisitance)值由0.682Ω下降至0.557Ω；外加逆向偏壓於-20V之漏電流(reverse leakage current)值由-0.943μA下降為-0.288μA。417nm發光波段之垂直式結構發光二極體於增加25及50對之藍光轉換層量子井結構之後，串聯電阻值由0.686Ω分別降低為0.550Ω與0.612Ω；於-20V外加逆向偏壓下漏電流亦由-1.639μA下降至-0.681μA及-0.362μA。表示添加藍/綠光多重量子井轉換層，能夠使元件結構應力降低，磊晶層品質獲得改善、晶格缺陷數目減少，電特性表現便較佳。藉由拉曼散射(Raman scattering)光譜量測所呈現之峰值位移趨勢，亦可驗證此一推論。

　　針對元件發光特性作探討，由於光子循環結構發光二極體之藍/綠光為光激發機制出光，光子激發轉換層使載子能夠較均勻分布於轉換層中各個量子井，相較於電注入機制，載子大部分集中於靠近元件p型區(p-side)之少數幾個量子井而言，主動區(active region)體積大幅提升，使得多重量子井結構中電子溢流(electron leakage)、歐傑複合(Auger recombination)效應及電流擁擠(current crowding)所致元件熱效應等現象減少。因此於高電流注入下，其效率衰退(efficiency droop)現象相較於垂直式結構發光二極體之電激發藍/綠光可獲得明顯的改善。因此透過光子循環結構之設計，利用光激發光取代電激發光機制，能夠作為改善氮化銦鎵/氮化鎵系列之藍/綠光發光二極體效率衰退現象之途徑。

In this thesis, we investigated the optical and electrical characteristics for photon-recycling structure light-emitting diodes (PRSLEDs). Comparing to conventional vertical light-emitting diodes (VLEDs), PRSLEDs had an additional multiple quantum well (MQW) converter above the device structures. Electrical characteristics of devices were analyzed by semiconductor parameters measurement, which demonstrated that PRSLEDs had better electrical performances compared to VLEDs. Because the MQW converter layer stacked on devices could reduce the strain-related stress of epitaxial structure. Then, the structure quality was improved and the crystal defects density decreased. While optical characteristics were analyzed by applying the Gaussian function fitting data of electroluminescence (EL) measurement. It showed that efficiency droop of electrically injected near ultraviolet (n-UV) light of PRSLEDs were improved, for its crystal quality was better than VLEDs aforementioned. Optically pumped blue/green light of PRSLEDs also showed potentially insignificant efficiency droop compared to direct blue/green VLEDs, for the volume of active region was increased by optical pumping mechanism, which reduced Auger recombination, carriers leakage, current crowding, and devices thermal effect, etc., effectively. In conclusion, the design of photon-recycling structure could improve LEDs electrical properties and effectively remedied efficiency droop of blue/green light by replacing the electric injection with optically pumped mechanism.

摘要 I
Abstract III
誌謝 IX
目錄 X
表目錄 XIII
圖目錄 XIV

第一章　序論 1
1.1 前言 1
1.2 研究動機 3

第二章　理論基礎與量測系統 6
2.1 理論基礎 6
2.1.1 發光二極體原理 6
2.1.2 垂直式結構發光二極體 10
2.1.3 光子循環結構發光二極體 14
2.1.4 應力 17
2.1.5 拉曼位移 20
2.1.6 量子侷限效應 24
2.1.7 效率衰退理論 28
2.2 量測系統 32
2.2.1 電流－電壓半導體特性量測系統 32
2.2.2 拉曼散射光譜儀量測系統 33
2.2.3 電激發光譜量測系統 34
2.2.4 光電流量測系統 35

第三章　元件設計與結構 36
3.1 元件磊晶結構 36
3.2 垂直式元件製程 41
3.3 元件設計與種類 44
3.3.1 垂直式結構發光二極體元件 44
3.3.2 光子循環結構發光二極體元件 47
3.3.3 元件試樣與外觀 50

第四章　數據分析與討論 54
4.1 垂直式結構與光循環結構發光二極體元件電特性之分析 54
4.2 垂直式結構與光循環結構發光二極體元件光特性之分析 59
4.3 針對垂直式結構與光循環結構發光二極體元件作變化溫度之光特性分析 85

第五章　結論與未來展望 93
5.1 結論 93
5.2 未來展望 94

參考文獻 96

[1]S. Nakamura, T. Mukai, and M. Senoh, “Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes, Appl. Phys. Lett., vol. 64, pp. 1687–1689, 1994.
[2]I. Vurgaftman, J. R. Meyer, and L. R. Ram-Mohan, “Band parameters for III–V compound semiconductors and their alloys, J. Appl. Phys., vol. 89, pp. 5815–5875, 2001.
[3]V. Y. Davydov, A. A. Klochikhin, R. P. Seisyan, V. V. Emtsev, S. V. Ivanov, F. Bechstedt, et al., “Absorption and emission of hexagonal InN. evidence of narrow fundamental band gap, phys. stat. sol. (b), vol. 229, pp. R1–R3, 2002.
[4]J. Wu, W. Walukiewicz, K. M. Yu, J. W. Ager, E. E. Haller, H. Lu, et al., “Unusual properties of the fundamental band gap of InN, Appl. Phys. Lett., vol. 80, pp. 3967–3969, 2002.
[5]T. Mukai, M. Yamada, and S. Nakamura, “Current and temperature dependences of electroluminescence of InGaN-based UV/blue/green light-emitting diodes, Jpn. J. Appl. Phys., vol. 37, pp. 1358–1361, 1998.
[6]T. Mukai, M. Yamada, and S. Nakamura, “Characteristics of InGaN-based UV/blue/green/amber/red light-emitting diodes, Jpn. J. Appl. Phys., vol. 38, pp. 3976–3981, 1999.
[7]S. J. Chang, W. C. Lai, Y. K. Su, J. F. Chen, C. H. Liu, and U. H. Liaw, “InGaN/GaN multiquantum well blue and green light emitting diodes, IEEE J. Sel. Topics Quantum Electron., vol. 8, pp. 278–283, 2002.
[8]S. W. Kaun, M. H. Wong, U. K. Mishra, and J. S. Speck, “Molecular beam epitaxy for high-performance Ga-face GaN electron devices, Semicond. Sci. Technol., vol. 28, pp. 074001-1–074001-15, 2013.
[9]T. Fujii, Y. Gao, R. Sharma, E. L. Hu, S. P. DenBaars, and S. Nakamura, “Increase in the extraction efficiency of GaN-based light-emitting diodes via surface roughening, Appl. Phys. Lett., vol. 84, pp. 855–857, 2004.
[10]O. B. Shchekin, J. E. Epler, T. A. Trottier, T. Margalith, D. A. Steigerwald, M. O. Holcomb, P. S. Martin, and M. R. Krames, “High performance thin-film flip-chip InGaN–GaN light-emitting diodes, Appl. Phys. Lett., vol. 89, pp. 071109-1–071109-3, 2006.
[11]J.-H. Ryou, W. Lee, J. Limb, D. Yoo, J. P. Liu, R. D. Dupuis, Z. H. Wu, A. M. Fischer, and F. A. Ponce, “Control of quantum-confined Stark effect in InGaN/GaN multiple quantum well active region by p-type layer for III-nitride-based visible light emitting diodes, Appl. Phys. Lett., vol. 92, pp. 101113-1–101113-3, 2008.
[12]A. S. Polkovnikov and G. G. Zegrya, “Auger recombination in semiconductor quantum wells, Phys. Rev. B, vol. 58, pp.4039–4056, 1998.
[13]K. A. Bulashevich and S. Yu. Karpov, “Is Auger recombination responsible for the efficiency rollover in III-nitride light-emitting diodes?, phys. stat. sol. (c), vol. 5, pp. 2066–2069, 2008.
[14]J. Hader, J. V. Moloney, B. Pasenow, S. W. Koch, M. Sabathil, N. Linder, and S. Lutgen, “On the importance of radiative and Auger losses in GaN-based quantum wells, Appl. Phys. Lett., vol. 92, pp. 261103-1–261103-3, 2008.
[15]E. T. Yu, X. Z. Dang, P. M. Asbeck, S. S. Lau, and G. J. Sullivan, “Spontaneous and piezoelectric polarization effects in III–V nitride heterostructures, J. Vac. Sci. Technol. B, vol.17, pp. 1742–1749, 1999.
[16]X. Guo and E. F. Schubert, “Current crowding in GaN/InGaN light emitting diodes on insulating substrates, J. Appl. Phys., vol. 90, pp. 4191–4195, 2001.
[17]X. Guo, J. W. Graff, and E. F. Schubert, “Photon-recycling semiconductor light-emitting diodes, IEDM Tech. Dig., vol. IEDM-99, pp. 600–605, 1999.
[18]J. I. Pankove, E. A. Miller, D. Richman, and J. E. Berkeyheiser, “Electroluminescence in GaN, J. Luminescence, vol. 4, pp. 63–66, 1971.
[19]S. Dhoble, H. Swart, and K. Park, Phosphate Phosphors for Solid-State Lighting, Springer, 2012.
[20]A. Laubsch, W. Bergbauer, M. Sabathil, M. Strassburg, H. Lugauer, M. Peter, T. Meyer, G. Brüderl, J. Wagner, N. Linder, K. Streubel, and B. Hahn, “Luminescence properties of thick InGaN quantum-wells, phys. stat. sol. (c), vol. 6, pp. S885–S888, 2009.
[21]C. S. Xia, Z. M. Simon Li, Z. Q. Li, Y. Sheng, Z. H. Zhang, W. Lu, and L. W. Cheng, “Optimal number of quantum wells for blue InGaN/GaN light-emitting diodes, Appl. Phys. Lett., vol. 100, pp. 263504-1–263504-3, 2012.
[22]S. Choi, H. J. Kim, S.-S. Kim, J. Liu, J. Kim, J.-H. Ryou, R. D. Dupuis, A. M. Fischer, and F. A. Ponce, “Improvement of peak quantum efficiency and efficiency droop in III-nitride visible light-emitting diodes with an InAlN electron-blocking layer, Appl. Phys. Lett., vol. 96, pp. 221105-1–221105-3, 2010.
[23]B. Damilano, P. Demolon, J. Brault, T. Huault, F. Natali, and J. Massies, “Blue-green and white color tuning of monolithic light emitting diodes, J. Appl. Phys., vol. 108, pp. 073115-1–073115-6, 2010.
[24]B. Damilano, N. Trad, J. Brault, P. Demolon, F. Natali, and J. Massies, “Color control in monolithic white light emitting diodes using a (Ga,In)N/GaN multiple quantum well light converter, phys. stat. sol. (a), vol. 209, pp. 465–468, 2012.
[25]E. F. Schubert, Light-Emitting Diodes, Cambridge University Press, 2nd ed. 2006.
[26]M. Fujita, “Silicon photonics: Nanocavity brightens silicon, Nat. Photonics, pp. 264–265, 2013.
[27]史光國，半導體發光二極體及固態照明，全華科技圖書股份有限公司，2005。
[28]施敏，半導體元件物理與製作技術，國立交通大學出版社，第二版，2002。
[29]郭浩中、賴芳儀、郭守義，LED原理與應用，五南圖書出版股份有限公司，2009。
[30]C. Y. Jia, C. T. Zhong, T. J. Yu, Z. Wang, Y. Z. Tong, and G. Y. Zhang, “Improvement of electrostatic discharge characteristics of InGaN/GaN MQWs light-emitting diodes by inserting an n+-InGaN electron injection layer and a p-InGaN/GaN hole injection layer, Semicond. Sci. Technol., vol. 27, pp. 065008-1–065008-5, 2012.
[31]W. S. Wong, T. Sands, N. W. Cheung, M. Kneissl, D. P. Bour, P. Mei, L. T. Romano, and N. M. Johnson, “InxGa1-xN light emitting diodes on Si substrates fabricated by Pd–In metal bonding and laser lift-off, Appl. Phys. Lett., vol. 77, pp. 2822–2824, 2000.
[32]W. Y. Lin, D. S. Wuu, K. F. Pan, S. H. Huang, C. E. Lee, W. K. Wang, S. C. Hsu, Y. Y. Su, S. Y. Huang, and R. H. Horng, “High-power GaN–mirror–Cu light-emitting diodes for vertical current injection using laser liftoff and electroplating techniques, IEEE Photon. Technol. Lett., vol. 17, pp. 1809–1811, 2005.
[33]Q.-Y. Tong and U. Gösele, Semiconductor wafer bonding: science and technology, John Wiley ＆ Sons, Inc., 1998.
[34]C. H. Chiu, C. E. Lee, C. L. Chao, B. S. Cheng, H. W. Huang, H. C. Kuo, T. C. Lu, S. C. Wang, W. L. Kuo, C. S. Hsiao, and S. Y. Chen, “Enhancement of light output intensity by integrating ZnO nanorod arrays on GaN-based LLO vertical LEDs, Electrochem. Solid-State Lett., vol. 11, pp. H84–H87, 2008.
[35]D.-F. Wang, F. Shiwei, C. Lu, A. Motayed, M. Jah, S. N. Mohammad, K. A. Jones, and L. Salamanca-Riba, “Low-resistance Ti/Al/Ti/Au multilayer ohmic contact to n-GaN, J. Appl. Phys., vol. 89, pp. 6214–6217, 2001.
[36]Z. F. Fan, S. N. Mohammad, W. Kim, Ö. Aktas, A. E. Botchkarev, and H. Morkoç, “Very low resistance multilayer Ohmic contact to n‐GaN, Appl. Phys. Lett., vol. 68, pp. 1672–1674, 1996.
[37]C. Z. Lu, H. N. Chen, X. L. Lv, X. S. Xie, and S. N. Mohammad, “Temperature and doping-dependent resistivity of Ti/Au/Pd/Au multilayer ohmic contact to n-GaN, J. Appl. Phys., vol. 91, pp. 9218–9224, 2002.
[38]Y. S. Zhao, D. L. Hibbard, H. P. Lee, K. Ma, W. So, and H. Liu, “Efficiency enhancement of InGaN/GaN light-emitting diodes with a back-surface distributed Bragg reflector, J. Electron. Mater., vol. 32, pp. 1523–1526, 2003.
[39]M. Sumiya, M. Tanaka, K. Ohtsuka, S. Fuke, T. Ohnishi, I. Ohkubo, M. Yoshimoto, H. Koinuma, and M. Kawasaki, “Analysis of the polar direction of GaN film growth by coaxial impact collision ion scattering spectroscopy, Appl. Phys. Lett., vol. 75, pp. 674–676, 1999.
[40]B. E. A. Saleh, M. C. Teich, Fundamentals of Photonics, John Wiley ＆ Sons, Inc., 2nd ed. 2007.
[41]S. Nakamura and G. Fasol, The Blue Laser Diode, Springer-Verlag, 1997.
[42]J. K. Sheu, S. J. Chang, C. H. Kuo, Y. K. Su, L. W. Wu, Y. C. Lin, W. C. Lai, J. M. Tsai, G. C. Chi, and R. K. Wu, “White-light emission from near UV InGaN-GaN LED chip precoated with blue/green/red phosphors, IEEE Photon. Technol. Lett., vol. 15, pp. 18–20, 2003.
[43]K. P. O’Donnell, R. W. Martin, and P. G. Middleton, “Origin of luminescence from InGaN diodes, Phys. Rev. Lett., vol. 82, pp. 237–240, 1999.
[44]F. Urbach, “The long-wavelength edge of photographic sensitivity and of the electronic absorption of solids, Phys. Rev., vol. 92, pp. 1324, 1953.
[45]L. Siozade, P. Disseix, A. Vasson, J. Leymarie, B. Damilano, N. Grandjean, and J. Massies, “Absorption and emission of (In,Ga)N/GaN quantum wells grown by molecular beam epitaxy, phys. stat. sol. (a), vol. 183, pp. 139–143, 2001.
[46]P. Bhattacharya, Semiconductor Optoelectronic Devices, Prentice Hall, Inc., 2nd ed. 1997.
[47]T.-M. Chou, User’s Manual for GAIN Program, Southern Methodist University, 2003.
[48]J. Piprek, Nitride Semiconductor Devices: Principles and Simulation, Wiley-VCH Verlag GmbH ＆ Co. KGaA, 2007.
[49]J. Singh, Electronic and Optoelectronic Properties of Semiconductor Structures, Cambridge University Press, 2003.
[50]A. Y. Kim, W. Gӧtz, D. A. Steigerwald, J. J. Wierer, N. F. Gardner, J. Sun, S. A. Stockman, P. S. Martin, M. R. Krames, R. S. Kern, and F. M. Steranka, “Performance of high-power AlInGaN light emitting diodes, phys. stat. sol. (a), vol. 188, pp. 15–21, 2001.
[51]C. Liu, W. N. Wang, P. A. Shields, S. Denchitcharoen, F. Causa, and D. E. W. Allsopp, “Improvement of efficiency droop in resonanace tunneling LEDs, Proc. SPIE, vol. 7058, pp. 70580D-1–70580D-8, 2008.
[52]S. Yamaguchi, M. Kariya, S. Nitta, H. Amano, and I. Akasaki, “Strain relief and its effect on the properties of GaN using isoelectronic In doping grown by metalorganic vapor phase epitaxy, Appl. Phys. Lett., vol. 75, pp. 4106–4108, 1999.
[53]N. Niu, H. B. Wang, J. P. Liu, N. X. Liu, Y. H. Xing, J. Han, J. Deng, and G. D. Shen, “Enhanced luminescence of InGaN/GaN multiple quantum wells by strain reduction, Solid-State Electron., vol. 51, pp. 860–864, 2007.
[54]D. J. Gardiner, Practical Raman spectroscopy, Springer-Verlag, 1989.
[55]D. Kirillov, H. Lee, and J. S. Harris, “Raman scattering study of GaN films, J. Appl. Phys., vol. 88, pp. 4058–4062, 1996.
[56]J. M. Zhang, T. Ruf, M. Cardona, O. Ambacher, M. Stutzmann, J.-M. Wagner, and F. Bechstedt, “Raman spectra of isotopic GaN, Phys. Rev. B, vol. 56, pp. 14399–14406, 1997.
[57]H. Harima, “Properties of GaN and related compounds studied by means of Raman scattering, J. Phys.: Condens. Matter, vol. 14, pp. R967–R993, 2002.
[58]P. Perlin, C. J. Carillon, J. P. Itie, A. S. Miguel, I. Grzegory, and A. Polian, “Raman scattering and x-ray-absorption spectroscopy in gallium nitride under high pressure, Phys. Rev. B, vol. 45, pp. 83–89, 1992.
[59]V. Yu. Davydov, Yu. E. Kitaev, I. N. Goncharuk, A. N. Smirnov, J. Graul, O. Semchinova, D. Uffmann, M. B. Smirnov, A. P. Mirgorodsky, and R. A. Evarestov, “Phonon dispersion and Raman scattering in hexagonal GaN and AlN, Phys. Rev. B, vol. 58, pp. 12899–12907, 1998.
[60]V. Yu. Davydov, V. V. Emtsev, I. N. Goncharuk, A. N. Smirnov, V. D. Petrikov, V. V. Mamutin, V. A. Vekshin, S. V. Ivanov, M. B. Smirnov, and T. Inushima, “Experimental and theoretical studies of phonons in hexagonal InN, Appl. Phys. Lett., vol. 75, pp. 3297–3299, 1999.
[61]J. Piprek, Semiconductor Optoelectronic Devices: Introduction to Physics and Simulation, Academic Press, 2003.
[62]A. E. Romanov, T. J. Baker, S. Nakamura, and J. S. Speck, “Strain-induced polarization in wurtzite III-nitride semipolar layers, J. Appl. Phys., vol. 100, pp. 023522-1–023522-10, 2006.
[63]T. Takeuchi, S. Sota, M. Katsuragawa, M. Komori, H. Takeuchi, H. Amano, and I. Akasaki, “Quantum-confined Stark effect due to piezoelectric fields in GaInN strained quantum wells, Jpn. J. Appl. Phys., vol. 36, pp. L382–L385, 1997.
[64]S. F. Chichibu, A. C. Abare, M. S. Minsky, S. Keller, S. B. Fleischer, J. E. Bowers, E. Hu, U. K. Mishra, L. A. Coldren, S. P. DenBaars, and T. Sota, “Effective band gap inhomogeneity and piezoelectric field in InGaN/GaN multiquantum well structures, Appl. Phys. Lett., vol. 73, pp. 2006–2008, 1998.
[65]P. Waltereit, O. Brandt, A. Trampert, H. T. Grahn, J. Menniger, M. Ramsteiner, M. Reiche, and K. H. Ploog, “Nitride semiconductors free of electrostatic field for efficient white light-emitting diodes, Nature, vol. 406, pp. 865–868, 2000.
[66]T. Takeuchi, C. Wetzel, S. Yamaguchi, H. Sakai, H. Amano, and I. Akasaki, “Determination of piezoelectric fields in strained GaInN quantum wells using the quantum-confined Stark effect, Appl. Phys. Lett., vol. 73, pp. 1691–1693, 1998.
[67]S. De, A. Layek, S. Bhattacharya, D. K. Das, A. Kadir, A. Bhattacharya, S. Dhar, and A. Chowdhury, “Quantum-confined stark effect in localized luminescent centers within InGaN/GaN quantum-well based light emitting diodes, Appl. Phys. Lett., vol. 101, pp. 121919-1–121919-5, 2012.
[68]R. W. Martin, P. G. Middleton, K. P. O’Donnell, and W. Van der Stricht, “Exciton localization and the Stokes’ shift in InGaN epilayers, Appl. Phys. Lett., vol. 74, pp. 263–265, 1999.
[69]E. Kuokstis, J. W. Yang, G. Simin, and M. A. Khan, “Two mechanisms of blueshift of edge emission in InGaN-based epilayers and multiple quantum wells, Appl. Phys. Lett., vol. 80, pp. 977–979, 2002.
[70]G. Verzellesi, D. Saguatti, M. Meneghini, F. Bertazzi, M. Goano, G. Meneghesso, and E. Zanoni, “Efficiency droop in InGaN/GaN blue light-emitting diodes: Physical mechanisms and remedies, J. Appl. Phys., vol. 114, pp. 071101-1–071101-14, 2013.
[71]J. Piprek, “Efficiency droop in nitride-based light-emitting diodes, phys. stat. sol. (a), vol. 207, pp. 2217–2225, 2010.
[72]Photoluminescence pinpoints Auger as the cause of LED droop, Compound Semiconductor, 2014.
[73]J. Hader, J. V. Moloney, and S. W. Koch, “Density-activated defect recombination as a possible explanation for the efficiency droop in GaN-based diodes, Appl. Phys. Lett., vol. 96, pp. 221106-1–221106-3, 2010.
[74]C. S. Xia, Z. M. Simon Li, Z. Q. Li, Y. Sheng, Z. H. Zhang, W. Lu, and L. W. Cheng, “Optimal number of quantum wells for blue InGaN/GaN light-emitting diodes, Appl. Phys. Lett., vol. 100, pp. 263504-1–263504-, 2012.
[75]D. S. Meyaard, Q. Shan, J. Cho, E. F. Schubert, S.-H. Han, M.-H. Kim, C. Sone, S. J. Oh, and J. K. Kim, “Temperature dependent efficiency droop in GaInN light-emitting diodes with different current densities, Appl. Phys. Lett., vol. 100, pp. 081106-1–081106-, 2012.
[76]M. F. Schubert, J. Xu, J. K. Kim, E. F. Schubert, M. H. Kim, S. Yoon, S. M. Lee, C. Sone, T. Sakong, and Y. Park, “Polarization-matched GaInN/ AlGaInN multi-quantum-well light-emitting diodes with reduced efficiency droop, Appl. Phys. Lett., vol. 93, pp. 041102-1–041102-, 2008.
[77]H. J. Chung, R. J. Choi, M. H. Kim, J. W. Han, Y. M. Park, Y. S. Kim, H. S. Paek, C. S. Sone, Y. J. Park, J. K. Kim, and E. F. Schubert, “Improved performance of GaN-based blue light emitting diodes with InGaN/GaN multilayer barriers, Appl. Phys. Lett., vol. 95, pp. 241109-1–241109-, 2009.
[78]C. H. Wang, S. P. Chang, P. H. Ku, J. C. Li, Y. P. Lan, C. C. Lin, H. C. Yang, H. C. Kuo, T. C. Lu, S. C. Wang, and C. Y. Chang, “Hole transport improvement in InGaN/GaN light-emitting diodes by graded-composition multiple quantum barriers, Appl. Phys. Lett., vol. 99, pp. 171106-1–171106-, 2011.
[79]J.-K. Sheu, F.-B. Chen, S.-H. Wu, M.-L. Lee, P.-C. Chen, and Y.-H. Yeh, “Vertical InGaN-based green-band solar cells operating under high solar concentration up to 300 suns, Opt. Express, vol. 22, pp. A1222–A1228, 2014.
[80]M. K. Kelly, O. Ambacher, R. Dimitrov, R. Handschuh, and M. Stutzmann, “Optical Process for liftoff of Group III-nitride films, phys. stat. sol. (a), vol. 159, pp. R3–R4, 1997.
[81]W. S. Wong, T. Sands, and N. W. Cheung, “Damage-free separation of GaN thin films from sapphire substrates, Appl. Phys. Lett., vol. 72, pp. 599–601, 1998.
[82]J.-K. Sheu, F.-B. Chen, W.-Y. Yen, Y.-C. Wang, C.-N. Liu, Y.-H. Yeh, and M.-L. Lee, “GaN-based photon-recycling green light-emitting diodes with vertical-conduction structure, Opt. Express, vol. 23, pp. A371–A381, 2015.
[83]J. K. Sheu, G. C. Chi, Y. K. Su, C. C. Liu, C. M. Chang, W. C. Hung, and M. J. Jou, “Luminescence of an InGaN/GaN multiple quantum wells light-emitting diode, Solid-State Electron., vol. 44, pp. 1055–1058, 2000.
[84]Y. L. Li, T. Gessmann, E. F. Schubert, and J. K. Sheu, “Carrier dynamics in nitride-based light-emitting p-n junction diodes with two active regions emitting at different wavelengths, J. Appl. Phys., vol. 94, pp. 2167–2172, 2003.
[85]S. C. Shei, J. K. Sheu, C. M. Tsai, W. C. Lai, M. L. Lee, and C. H. Kuo, “Emission mechanism of mixed-color InGaN/GaN multi-quantum well light-emitting diodes, Jpn. J. Appl. Phys., vol. 45, pp. 2463–2466, 2006.
[86]D.-S. Shin, J.-I. Lee, and J.-I, Shim, “Systematic analysis of the photocurrent spectroscopy on InGaN/GaN blue light-emitting diodes, IEEE J. Quantum. Electron., vol. 49, pp. 1062–1065, 2013.
[87]J. H. Na, R. A. Taylor, K. H. Lee, T. Wang, A. Tahraoui, P. Parbrook, A. M. Fox, S. N. Yi, Y. S. Park, J. W. Choi, and J. S. Lee, “Dependence of carrier localization in InGaN/GaN multiple-quantum wells on well thickness, Appl. Phys. Lett., vol. 89, pp. 253120-1–253120-3, 2006.
[88]F. K. Yam and Z. Hassan, “InGaN: An overview of the growth kinetics, physical properties and emission mechanisms, Superlattices Microstruct., vol. 43, pp. 1–23, 2008.
[89]D. Schiavon, M. Binder, A. Loeffler, and M. Peter, “Optically pumped GaInN/GaN multiple quantum wells for the realization of efficient green light-emitting devices, Appl. Phys. Lett., vol. 102, pp. 113509-1–113509-4, 2013.
[90]S. Nakamura, M. Senoh, N. Iwasa, and S. 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.