在本論文中，為提升氮化鎵系發光二極體體之光萃取效率，本研究研製一系列結合銀奈米顆粒、鋁反射背板、氧化鎵表面披覆層，以及埋藏式電流阻擋層之氮化鎵系發光二極體，其中採用三種半導體性金屬氧化物薄膜作為埋藏式電流阻擋層材料，分別為氧化鋅錫、氧化鋁鎵及氧化銦鎵鋅。以此複合結構為主軸，進一步的提出奈米材料應用及元件製程技術，其中包含使用共濺鍍薄膜沉積系統沉積氧化鋅錫、氧化鋁鎵、氧化銦鎵鋅及氧化鎵，使用熱蒸鍍系統及快速熱退火製作銀奈米顆粒及鋁反射背板。本研究對複合結構式氮化鎵系發光二極體之光電特性，及各種特定結構之製備方式皆有深入且詳細的研究及探討。最後，將在發光二極體上表現良好的材料氧化銦鎵鋅薄膜使用在氣體感測器上，並結合鈀奈米顆粒與銀奈米顆粒修飾，展現出優異的感測響應、選擇性與長期穩定性。此外，該元件亦具備結構簡單、製程成本低等優勢，展現其在未來應用上的潛力。
在第二章中，使用熱蒸鍍系統沉積厚度為2奈米銀金屬薄膜，透過快速熱退火使銀金屬薄膜團簇為銀奈米顆粒，光子在通過銀奈米顆粒時會發生散射，有助於改變光的行徑方向，進而降低被不透明電極吸收的可能性。由於氧化鋅錫的特性，做為電流阻擋層的時候可以提升電流擴散現象以提升光性。本研究使用的埋藏式電流阻擋層相比於傳統電流阻擋層在電流擴散能力方面又能進一步提升，在元件光性及電性上都表現出色。鋁反射背板可以使朝元件底部發射的光反射，有助於減少被底部基板吸收的光。氧化鎵表面披覆層有助於降低元件的表面漏電流以及Fresnel光損失(Fresnel loss)並改善光特性。經過一系列的實驗，結合了銀奈米顆粒、氧化鋅錫埋藏式電流阻擋層、鋁反射背板及氧化鎵表面披覆層的氮化鎵系發光二極體擁有最佳的特性。相較於傳統平面式氮化鎵系發光二極體，此元件在光輸出功率、光通量、外部量子效率及遠場效應強度分別提升27.94%、2.38%、27.93%及39.56%。
第三章延續此架構，將埋藏式電流阻擋層使用的材料由氧化鋅錫改成氧化鋁鎵，厚度約為10奈米。相較於傳統平面式氮化鎵系發光二極體，最佳元件在光輸出功率、光通量、外部量子效率及遠場效應強度分別提升29.58%、10.68%、29.59%及36.26%。
第四章同樣延續第二章所使用之結構，將埋藏式電流阻擋層的材料由氧化鋅錫改成氧化銦鎵鋅，厚度約為35奈米。相較於傳統平面式氮化鎵系發光二極體，最佳元件在光輸出功率、光通量、外部量子效率及遠場效應強度分別提升37.51%、39.57%、37.48%及36.03%。
在第五章中，將前一章表現良好的氧化銦鎵鋅薄膜材料應用於氣體感測器，並利用鈀奈米顆粒與銀奈米顆粒修飾，對於氫氣有良好的感測特性，在275℃環境下，通入濃度為1%的氫氣，感測響應為1.44×106，吸附以及脫附時間分別為91秒和3秒，同時對氫氣具有出色的選擇性和穩定性以及0.1ppm的極低檢測極限。
本研究論文中所研製之高品質氮化鎵系發光二極體，在元件光性及電性上皆具顯著優勢，且能有效降低表面漏電流與Fresnel光損失。同時，延伸應用於氣體感測領域之元件亦展現高感測響應、選擇性佳、穩定度高、結構簡易及製程成本低等特性，具備良好之商業應用潛力。

In this thesis, to enhance the light extraction efficiency (LEE) of GaN-based light-emitting diodes (LEDs), a series of devices were developed featuring a composite structure consisting of silver nanoparticles (Ag NPs), an aluminum backside reflector (Al BR), a gallium oxide (Ga2O3) surface passivation layer, and a buried current-blocking layer (B-CBL). Three different types of semiconducting metal oxide (SMO) thin films, zinc tin oxide (ZTO), aluminum gallium oxide (AGO), and indium gallium zinc oxide (IGZO), were employed as the B-CBL materials. Based on this composite structure, the study further proposed novel applications of nanomaterials and device fabrication techniques, including the deposition of ZTO, AGO, IGZO, and Ga2O3 using a co-sputtering system, and the fabrication of Ag NPs and Al BR via thermal evaporation (TE) and rapid thermal annealing (RTA). This work conducted a comprehensive investigation into the optoelectronic properties of the composite GaN-based LEDs and examined the fabrication procedures for each specific structure in detail. Furthermore, the IGZO thin film, which demonstrated superior performance in LED applications, was employed in gas sensor devices. Modified with palladium (Pd ) and silver (Ag) nanoparticles, the sensor exhibited excellent sensing response, selectivity, and stability characteristics. In addition, the device features a simple structure, low fabrication cost, and straightforward process flow, indicating its strong potential for future applications.
In Chapter 2, a 2 nm silver film was deposited using a thermal evaporation system and subsequently annealed using RTA to form Ag NPs. The nanoparticles scatter incident photons, altering their propagation path and thereby reducing absorption by opaque electrodes. Due to the electrical characteristics of ZTO, its use as a current blocking layer facilitates lateral current spreading, thereby improving the optical properties of the device. Compared with conventional CBLs, the buried-current blocking layer demonstrated further enhancements in current spreading, leading to significant improvements in both the optical and electrical characteristics of the device. The Al BR reflected downward-emitted photons, mitigating optical losses at the substrate. The Ga2O3 surface passivation layer helped suppress surface leakage current and Fresnel loss, further improving optical performance. Experimental results revealed that the GaN-based LED device incorporating Ag NPs, ZTO B-CBL, Al BR, and Ga2O3 surface layer exhibited the best overall performance. Compared to the conventional planar GaN-based LED, the optimized device showed enhancements of 27.94% in light output power, 2.38% in luminous flux, 27.93% in external quantum efficiency (EQE), and 39.56% in far-field intensity.
In Chapter 3, the ZTO B-CBL was replaced with a 10 nm thick AGO layer. Compared with the conventional LED, the optimized device showed respective improvements of 29.58% in light output power, 10.68% in luminous flux, 29.59% in EQE, and 36.26% in far-field intensity.
In Chapter 4, the B-CBL material was further substituted with a 35 nm thick IGZO layer. Compared to the conventional LED, the optimized device achieved enhancements of 37.51% in light output power, 39.57% in luminous flux, 37.48% in EQE, and 36.03% in far-field intensity.
Chapter 5, the IGZO thin film, which showed the outstanding performance in the LED device, was applied to hydrogen gas sensing. By incorporating Pd and Ag nanoparticles, the sensor exhibited excellent hydrogen detection characteristics. At an operating temperature of 275 °C under a 1% H2/air environment, the sensing response reached 1.44 × 106, with response and recovery times of 91 seconds and 3 seconds, respectively. The sensor also demonstrated outstanding selectivity, long-term stability, and an ultra-low detection limit of 0.1 ppm.
In conclusion, the high-performance GaN-based LEDs developed in this study exhibited superior optical and electrical performance, along with reduced surface leakage current and Fresnel loss. As for the gas sensor devices, the proposed structure offers multiple advantages, including high sensing response, excellent selectivity, long-term stability, structural simplicity, low fabrication cost, and ease of manufacturing. These attributes demonstrate the promising potential of the proposed devices for commercial applications.

[1] M.H. Crawford, "LEDs for Solid-State Lighting: Performance Challenges and Recent Advances," IEEE Journal of Selected Topics in Quantum Electronics, vol. 15, pp. 1028-1040, 2009.
[2] E.F. Schubert, and J.K. Kim, "Solid-State Light Sources Getting Smart," Science, vol. 308, pp. 1274, 2005.
[3] H.P. Maruska, and J.J. Tietjen, "THE PREPARATION AND PROPERTIES OF VAPOR‐DEPOSITED SINGLE‐CRYSTAL‐LINE GaN," Applied Physics Letters, vol. 15, pp. 327-329, 1969.
[4] H.P. Maruska, D.A. Stevenson, and J.I. Pankove, "Violet luminescence of Mg‐doped GaN," Applied Physics Letters, vol. 22, pp. 303-305, 1973.
[5] M. Ilegems, and R. Dingle, "Luminescence of Be‐ and Mg‐doped GaN," Journal of Applied Physics, vol. 44, pp. 4234-4235, 1973.
[6] H.P. Maruska, and D.A. Stevenson, "Mechanism of light production in metal-insulator-semiconductor diodes; GaN:Mg violet light-emitting diodes," Solid-State Electronics, vol. 17, pp. 1171-1179, 1974.
[7] H. Amano, M. Kito, K. Hiramatsu, and I. Akasaki, "P-Type Conduction in Mg-Doped GaN Treated with Low-Energy Electron Beam Irradiation (LEEBI)," Japanese Journal of Applied Physics, vol. 28, pp. L2112-L2114, 1989.
[8] S. Nakamura, T. Mukai, M. Senoh, and N. Iwasa, "Thermal Annealing Effects on P-Type Mg-Doped GaN Films," Japanese Journal of Applied Physics, vol. 31, pp. L139-L142, 1992.
[9] S. Nakamura, N. Iwasa, M. Senoh, and T. Mukai, "Hole Compensation Mechanism of P-Type GaN Films," Japanese Journal of Applied Physics, vol. 31, pp. 1258-1266, 1992.
[10] S. Yoshida, S. Misawa, and S. Gonda, "Improvements on the electrical and luminescent properties of reactive molecular beam epitaxially grown GaN films by using AlN‐coated sapphire substrates," Applied Physics Letters, vol. 42, pp. 427-429, 1983.
[11] H. Amano, N. Sawaki, I. Akasaki, and Y. Toyoda, "Metalorganic vapor phase epitaxial growth of a high quality GaN film using an AlN buffer layer," Applied Physics Letters, vol. 48, pp. 353-355, 1986.
[12] S. Nakamura, "GaN Growth Using GaN Buffer Layer," Japanese Journal of Applied Physics, vol. 30, pp. L1705-L1707, 1991.
[13] S. Nakamura, T. Mukai, and M. Senoh, "In situ monitoring and Hall measurements of GaN grown with GaN buffer layers," Journal of Applied Physics, vol. 71, pp. 5543-5549, 1992.
[14] S. Nakamura, M. Senoh, N. Iwasa, and S.-i. Nagahama, "High-Brightness InGaN Blue, Green and Yellow Light-Emitting Diodes with Quantum Well Structures," Japanese Journal of Applied Physics, vol. 34, pp. L797-L799, 1995.
[15] M.M. Oka, A. Nakada, K. Tomita, T. Shibata, T. Ohmi, and T. Nitta, "Reducing Reverse-Bias Current in 450°C-Annealed n+p Junction by Hydrogen Radical Sintering," Japanese Journal of Applied Physics, vol. 34, pp. 796-799, 1995.
[16] J.I. Pankove, E.A. Miller, and J.E. Berkeyheiser, Electroluminescence in GaN, in: F. Williams, B. Baron, M. Martens, S.P. Varma (Eds.), Luminescence of Crystals, Molecules, and Solutions, Springer US, Boston, MA, 1973, pp. 426-430.
[17] S. Nakamura, T. Mukai, and M. Senoh, "High-Power GaN P-N Junction Blue-Light-Emitting Diodes," Japanese Journal of Applied Physics, vol. 30, pp. L1998-L2001, 1991.
[18] S. Nakamura, M. Senoh, and T. Mukai, "P-GaN/N-InGaN/N-GaN Double-Heterostructure Blue-Light-Emitting Diodes," Japanese Journal of Applied Physics, vol. 32, pp. L8-L11, 1993.
[19] S. Nakamura, T. Mukai, and M. Senoh, "Candela‐class high‐brightness InGaN/AlGaN double‐heterostructure blue‐light‐emitting diodes," Applied Physics Letters, vol. 64, pp. 1687-1689, 1994.
[20] Y. Nanishi, "The birth of the blue LED," Nature Photonics, vol. 8, pp. 884-886, 2014.
[21] D.W. Runton, B. Trabert, J.B. Shealy, and R. Vetury, "History of GaN: High-Power RF Gallium Nitride (GaN) from Infancy to Manufacturable Process and Beyond," IEEE Microwave Magazine, vol. 14, pp. 82-93, 2013.
[22] D. Shi, S. Feng, Y. Qiao, and P. Wen, "The research on temperature distribution of GaN-based blue laser diode," Solid-State Electronics, vol. 109, pp. 25-28, 2015.
[23] S. Nakamura, "Background Story of the Invention of Efficient InGaN Blue-Light-Emitting Diodes (Nobel Lecture)," Angewandte Chemie International Edition, vol. 54, pp. 7770-7788, 2015.
[24] S. Nakamura, "Nobel Lecture: Background story of the invention of efficient blue InGaN light emitting diodes," Reviews of Modern Physics, vol. 87, pp. 1139-1151, 2015.
[25] I.E. Titkov, S.Y. Karpov, A. Yadav, V.L. Zerova, M. Zulonas, B. Galler, M. Strassburg, I. Pietzonka, H.J. Lugauer, and E.U. Rafailov, "Temperature-Dependent Internal Quantum Efficiency of Blue High-Brightness Light-Emitting Diodes," IEEE Journal of Quantum Electronics, vol. 50, pp. 911-920, 2014.
[26] I. Schnitzer, E. Yablonovitch, C. Caneau, T.J. Gmitter, and A. Scherer, "30% externalquantum efficiency from surface textured, thin‐film light‐emitting diodes," Applied Physics Letters, vol. 63, pp. 2174-2176, 1993.
[27] C.P. Kuo, R.M. Fletcher, T.D. Osentowski, M.C. Lardizabal, M.G. Craford, and V.M. Robbins, "High performance AlGaInP visible light‐emitting diodes," Applied Physics Letters, vol. 57, pp. 2937-2939, 1990.
[28] Y.J. Liu, T.Y. Tsai, C.H. Yen, L.Y. Chen, T.H. Tsai, and W.C. Liu, "Characteristics of a GaN-Based Light-Emitting Diode With an Inserted p-GaN/i-InGaN Superlattice Structure," IEEE Journal of Quantum Electronics, vol. 46, pp. 492-498, 2010.
[29] A. Billeb, W. Grieshaber, D. Stocker, E.F. Schubert, and R.F. Karlicek, "Microcavity effects in GaN epitaxial films and in Ag/GaN/sapphire structures," Applied Physics Letters, vol. 70, pp. 2790-2792, 1997.
[30] H. Chul, L. Ji-Myon, K. Dong-Joon, and P. Seong-Ju, Current blocking layer in GaN light-emitting diode, Proc.SPIE2001.
[31] C. Huh, J.-M. Lee, D.-J. Kim, and S.-J. Park, "Improvement in light-output efficiency of InGaN/GaN multiple-quantum well light-emitting diodes by current blocking layer," Journal of Applied Physics, vol. 92, pp. 2248-2250, 2002.
[32] S. Chen, J. R. Manders, S.-W. Tsang, and F. So, "Metal oxides for interface engineering in polymer solar cells," Journal of Materials Chemistry, vol. 22, pp. 24202-24212, 2012.
[33] Y.-J. Lee, Z.-P. Yang, P.-G. Chen, Y.-A. Hsieh, Y.-C. Yao, M.-H. Liao, M.-H. Lee, M.-T. Wang, and J.-M. Hwang, "Monolithic integration of GaN-based light-emitting diodes and metal-oxide-semiconductor field-effect transistors," Optical Society of America, vol. 22, pp. A1589-A1595, 2014.
[34] A.A. Tomchenko, G.P. Harmer, B.T. Marquis, and J.W. Allen, "Semiconducting metal oxide sensor array for the selective detection of combustion gases," Sensors and Actuators B, vol. 93, pp. 126-134, 2003.
[35] E.E. Perl, J. Simon, J.F. Geisz, W. Olavarria, M. Young, A. Duda, D.J. Friedman, and M.A. Steiner, "Development of High-Bandgap AlGaInP Solar Cells Grown by Organometallic Vapor-Phase Epitaxy," IEEE Journal of Photovoltaics, vol. 6, pp. 770-776, 2016.
[36] V.S. Robert, High-brightness LED market overview, Proc.SPIE2001.
[37] A. Barhoumi, G. Leroy, B. Duponchel, J. Gest, L. Yang, N. Waldhoff, and S. Guermazi, "Aluminum doped ZnO thin films deposited by direct current sputtering: Structural and optical properties," Superlattices and Microstructures, vol. 82, pp. 483-498, 2015.
[38] T. Mukai, M. Yamada, and S. Nakamura, "Characteristics of InGaN-Based UV/Blue/Green/Amber/Red Light-Emitting Diodes," Japanese Journal of Applied Physics, vol. 38, pp. 3976-3981, 1999.
[39] Y. Shimizu, N. Kuwano, T. Hyodo, and M. Egashira, “High H2 sensing performance of anodically oxidized TiO2 film contacted with Pd,” Sens. Actuators B Chem., vol. 83, pp. 195-201, 2002.
[40] Y. C. Yang, J.S. Niu, and W.C. Liu, “Study of a palladium nanoparticle/indium oxide-based hydrogen gas sensor,” IEEE Trans. Electron Devices, vol. 69, pp. 318-324, 2021.
[41] C. Xie, L. Xiao, M. Hu, Z. Bai, X. Xia, and D. Zeng, “Fabrication and formaldehyde gas-sensing property of ZnO–MnO2 coplanar gas sensor arrays,” Sens. Actuators B Chem., vol. 145, pp. 457-463, 2010.
[42] P. C. Yao, J. S. Niu, G. Y. Dai, J. J. Jian, W. C. Hsu, K. W. Lin, and W. C. Liu, “Ammonia sensing characteristics of an ITO-V2O5 based chemoresistive dual-type gas sensors (CDGS) decorated with platinum nanoparticles,” Sens. Actuators B Chem., vol. 392, pp. 134071, 2023.
[43] Y. H. Choi, D. H. Kim, S. H. Hong, and K. S. Hong, “H2 and C2H5OH sensing characteristics of mesoporous p-type CuO films prepared via a novel precursor-based ink solution route,” Sens. Actuators B Chem., vol. 178, pp. 395-403, 2013.
[44] C. W. Na, H. S. Woo, I. D. Kim, and J. H. Lee, “Selective detection of NO2 and C2H5OH using a Co3O4-decorated ZnO nanowire network sensor,” Chem. Commun., vol. 47, pp. 5148-5150, 2011.
[45] M. Koike, N. Shibata, H. Kato, and Y. Takahashi, "Development of high efficiency GaN-based multiquantum-well light-emitting diodes and their applications," IEEE Journal of Selected Topics in Quantum Electronics, vol. 8, pp. 271-277, 2002.
[46] S.-C. Tsai, M.-J. Li, H.-C. Fang, C.-H. Tu, and C.-P. Liu, "Efficiency enhancement of blue light emitting diodes by eliminating V-defects from InGaN/GaN multiple quantum well structures through GaN capping layer control," Applied Surface Science, vol. 439, pp. 1127-1132, 2018.
[47] B.R. Lee, T.H. Lee, K.-R. Son, and T.G. Kim, "ITO/Ag/AlN/Al2O3 multilayer electrodes with conductive channels: Application in ultraviolet light-emitting diodes," Journal of Alloys and Compounds, vol. 741, pp. 21-27, 2018.
[48] [40] 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," Journal of Display Technology, vol. 3, pp. 160-175, 2007.
[49] M. Zhang, Y. Li, Q. Li, X. Su, S. Wang, L. Feng, Z. Tian, M. Guo, G. Zhang, W. Ding, and F. Yun, "Characteristics of GaN-based 500 nm light-emitting diodes with embedded hemispherical air-cavity structure," Journal of Applied Physics, vol. 123, pp. 125702, 2018.
[50] A.I. Zhmakin, "Enhancement of light extraction from light emitting diodes," Physics Reports, vol. 498, pp. 189-241, 2011.
[51] C. Liao, Y. Chang, C. Ho, and M. Wu, "High-Speed GaN-Based Blue Light-Emitting Diodes With Gallium-Doped ZnO Current Spreading Layer," IEEE Electron Device Letters, vol. 34, pp. 611-613, 2013.
[52] P. Zuo, B. Zhao, S. Yan, G. Yue, H. Yang, Y. Li, H. Wu, Y. Jiang, H. Jia, J. Zhou, and H. Chen, "Improved optical and electrical performances of GaN-based light-emitting diodes with nano truncated cone SiO2 passivation layer," Optical and Quantum Electronics, vol. 48, pp. 288, 2016.
[53] S. Zhou, B. Cao, S. Liu, and H. Ding, "Improved light extraction efficiency of GaN-based LEDs with patterned sapphire substrate and patterned ITO," Optics & Laser Technology, vol. 44, pp. 2302-2305, 2012.
[54] Y.-C. Yao, J.-M. Hwang, Z.-P. Yang, J.-Y. Haung, C.-C. Lin, W.-C. Shen, C.-Y. Chou, M.-T. Wang, C.-Y. Huang, C.-Y. Chen, M.-T. Tsai, T.-N. Lin, J.-L. Shen, and Y.-J. Lee, "Enhanced external quantum efficiency in GaN-based vertical-type light-emitting diodes by localized surface plasmons," Scientific Reports, vol. 6, pp. 22659, 2016.
[55] C. Chen, and W. Liu, "Light Extraction Enhancement of GaN-Based Light-Emitting Diodes With Textured Sidewalls and ICP-Transferred Nanohemispherical Backside Reflector," IEEE Transactions on Electron Devices, vol. 64, pp. 3672-3677, 2017.
[56] J. Liou, C. Chen, P. Chou, S. Cheng, J. Tsai, R. Liu, and W. Liu, "Effects of the Use of an Aluminum Reflecting and an SiO2 Insulating Layers (RIL) on the Performance of a GaN-Based Light-Emitting Diode With the Naturally Textured p-GaN Surface," IEEE Transactions on Electron Devices, vol. 60, pp. 2282-2289, 2013.
[57] F. Lai, S.C. Ling, C.E. Hsieh, T.H. Hsueh, H. Kuo, and T. Lu, "Extraction Efficiency Enhancement of GaN-Based Light-Emitting Diodes by Microhole Array and Roughened Surface Oxide," IEEE Electron Device Letters, vol. 30, pp. 496-498, 2009.
[58] W. Park, and J.-B. Lee, "Mechanically tunable photonic crystal structure," Applied Physics Letters, vol. 85, pp. 4845-4847, 2004.
[59] B. Cao, S. Li, R. Hu, S. Zhou, Y. Sun, Z. Gan, and S. Liu, "Effects of current crowding on light extraction efficiency of conventional GaN-based light-emitting diodes," Opt. Express, vol. 21, pp. 25381-25388, 2013.
[60] J.-S. Park, J. Han, and T.-Y. Seong, “Improving the output power of GaN-based light-emitting diode using Ag particles embedded within a SiO2 current blocking layer,” Superlattice. Microst., vol. 83, pp. 361-366, 2015.
[61] V.K. Malyutenko, A.D. Podoltsev, and O.Y. Malyutenko, "Current crowding impact at spatially and temporarily resolved thermal characters of large-area AlGaInP light emitting diodes operating in dimming/flashing modes," Journal of Applied Physics, vol. 118, pp. 153105, 2015.
[62] Y.Y. Kudryk, A.K. Tkachenko, and A.V. Zinovchuk, "Temperature-dependent efficiency droop in InGaN-based light-emitting diodes induced by current crowding," Semiconductor Science and Technology, vol. 27, pp. 055013, 2012.
[63] Y.-C. Lee, F.-S. Hwu, M.-C. Yang, and C.-Y. Lin, "Experimental and Numerical Analysis of p-Electrode Patterns on the Lateral GaN-Based LEDs," J. Lightwave Technol., vol. 32, pp. 2643-2648, 2014.
[64] S. Zhou, M. Liu, H. Xu, Y. Liu, Y. Gao, X. Ding, S. Lan, Y. Fan, C. Gui, and S. Liu, "High-efficiency GaN-based LED with patterned SiO2 current blocking layer deposited on patterned ITO," Optics & Laser Technology, vol. 109, pp. 627-632, 2019.
[65] J.-S. Park, Y.H. Sung, J.-Y. Na, D. Kang, S.-K. Kim, H. Lee, and T.-Y. Seong, "Use of a patterned current blocking layer to enhance the light output power of InGaN-based light-emitting diodes," Opt. Express, vol. 25, pp. 17556-17561, 2017.
[66] H.W. Huang, F.I. Lai, J.K. Huang, C.H. Lin, K.Y. Lee, C.F. Lin, C.C. Yu, and H.C. Kuo, "Enhancement of light output power of GaN-based light-emitting diodes using a SiO2 nano-scale structure on a p-GaN surface," Semiconductor Science and Technology, vol. 25, pp. 065007, 2010.
[67] B.J. Kim, H. Jung, J. Shin, M.A. Mastro, C.R. Eddy, J.K. Hite, S.H. Kim, J. Bang, and J. Kim, "Enhancement of light extraction efficiency of ultraviolet light emitting diodes by patterning of SiO2 nanosphere arrays," Thin Solid Films, vol. 517, pp. 2742-2744, 2009.
[68] K.M. Chang, C.C. Lang, and C.C. Cheng, "The Silicon Nitride Film Formed by ECR-CVD for GaN-Based LED Passivation," physical status solid (a), vol. 188, pp. 175-178, 2001.
[69] X. Da, X. Guo, L. Dong, Y. Song, W. Ai, and G. Shen, "The silicon oxynitride layer deposited at low temperature for high-brightness GaN-based light-emitting diodes," Solid-State Electronics, vol. 50, pp. 508-510, 2006.
[70] S.-J. So, and C.-B. Park, "Improvement of brightness with Al2O3 passivation layers on the surface of InGaN/GaN-based light-emitting diode chips," Thin Solid Films, vol. 516, pp. 2031-2034, 2008.
[71] C.M. Yang, D.S. Kim, S.G. Lee, J.H. Lee, Y.S. Lee, and J.H. Lee, "Improvement in Electrical and Optical Performances of GaN-Based LED With SiO2/ Al2O3 Double Dielectric Stack Layer," IEEE Electron Device Letters, vol. 33, pp. 564-566, 2012.
[72] H. Guo, X. Zhang, H. Chen, P. Zhang, H. Liu, H. Chang, W. Zhao, Q. Liao, and Y. Cui, "High performance GaN-based LEDs on patterned sapphire substrate with patterned composite SiO2/Al2O3 passivation layers and TiO2/Al2O3 DBR backside reflector," Opt. Express, vol. 21, pp. 21456-21465, 2013.
[73] C.H. Chang, Y.L. Lee, Z.F. Wang, R.C. Liu, J.H. Tsai, and W.C. Liu, "Performance Improvement of GaN-Based Light-Emitting Diodes With a Microhole Array, 45° Sidewalls, and a SiO2 Nanoparticle/Microsphere Passivation Layer," IEEE Transactions on Electron Devices, vol. 66, pp. 505-511, 2019.
[74] Z. Wang, and W. Liu, "Influences of Microhole Depth and SiO2 Nanoparticle/Microsphere Passivation Layer on the Performance of GaN-Based Light-Emitting Diodes," IEEE Transactions on Electron Devices, vol. 66, pp. 4211-4215, 2019.
[75] Y. Chang, J. Liou, and W. Liu, "Improved Light Extraction Efficiency of a High-Power GaN-Based Light-Emitting Diode With a Three-Dimensional-Photonic Crystal (3-D-PhC) Backside Reflector," IEEE Electron Device Letters, vol. 34, pp. 777-779, 2013.
[76] S.-H. Han, D.-Y. Lee, S.-J. Lee, C.-Y. Cho, M.-K. Kwon, S.P. Lee, D.Y. Noh, D.-J. Kim, Y.C. Kim, and S.-J. Park, "Effect of electron blocking layer on efficiency droop in InGaN/GaN multiple quantum well light-emitting diodes," Applied Physics Letters, vol. 94, pp. 231123, 2009.
[77] C.C. Kao, Y.K. Su, and C.L. Lin, "Enhancement of Light Output Power of GaN-Based Light-Emitting Diodes by a Reflective Current Blocking Layer," IEEE Photonics Technology Letters, vol. 23, pp. 986-988, 2011.
[78] J. Piprek, "Efficiency droop in nitride-based light-emitting diodes," Physica Status Solidi A, vol. 207, pp. 2217-2225, 2010.
[79] M.F. Schubert, S. Chhajed, J.K. Kim, and E.F. Schubert, "Effect of dislocation density on efficiency droop in GaInNGaN light-emitting diodes," Applied Physics Letters, vol. 91, pp. 231114-231116, 2007.
[80] Y. L. Li, Y. R. Huang, Y. H. Lai, Y. L. Li, Y. R. Huang, and Y. H. Lai, "Efficiency droop behaviors of InGaNGaN multiple-quantum-well light-emitting diodes with varying quantum well thickness," Applied Physics Letters, vol. 91, pp. 181113-181115, 2007.
[81] Y. Cheng, T. Zhan, J. Ma, L. Zhang, Z. Si, X. Yi, G. Wang, and J. Li "Improved performance of lateral GaN-based light emitting diodes with novel buried CBL structure in ITO film and reflective electrodes," Materials Science in Semiconductor Processing, vol. 17, pp. 100-103, 2014.
[82] Y. Chang, J. Liou, and W. Liu, "Improved Light Extraction Efficiency of a High Power GaN-Based Light-Emitting Diode With a Three-Dimensional-Photonic Crystal (3-D-PhC) Backside Reflector," IEEE Electron Device Letters, vol. 34, pp. 777-779, 2013.
[83] D. Vanderbilt, X. Zhao, and D. Ceresoli, "Structural and dielectric properties of crystalline and amorphous ZrO2," Thin Solid Films, vol. 486, pp. 125-128, 2005.
[84] J.K. Sheu, I.H. Hung, W.C. Lai, S.C. Shei, and M.L. Lee, "Enhancement in output power of blue gallium nitride-based light-emitting diodes with omnidirectional metal reflector under electrode pads," Applied Physics Letters, vol. 93, pp. 103507, 2008.
[85] S.J. Chang, C.F. Shen, M.H. Hsieh, C.T. Kuo, T.K. Ko, W.S. Chen, and S.C. Shei, "Nitride-Based LEDs With a Hybrid Al Mirror + TiO2 / SiO2 DBR Backside Reflector," J. Lightwave Technol., vol. 26, pp. 3131-3136, 2008.
[86] B. Yao, X. Hu, J. Liu, K. Chen, and J. Liu, "Preparation and properties of high refractive index ZrO2 nano-hybrid materials," Materials Letters, vol. 261, pp. 126878, 2020.
[87] Q. Zhang, X. Li, J. Shen, G. Wu, J. Wang, and L. Chen, "ZrO2 thin films and ZrO2/SiO2 optical reflection filters deposited by sol–gel method," Materials Letters, vol. 45, pp. 311-314, 2000.
[88] H. Gao, F. Yan, Y. Zhang, J. Li, Y. Zeng, and G. Wang, "Enhancement of the light output power of InGaN/GaN light-emitting diodes grown on pyramidal patterned sapphire substrates in the micro- and nanoscale," Journal of Applied Physics, vol. 103, pp. 014314, 2008.
[89] C.C. Hsu, Y.R. Hou, J.S. Niu, and W.C. Liu, "Study of a GaN-Based Light-Emitting Diode With a Ga2O3 Current Blocking Layer and a Ga2O3 Surface Passivation Layer," IEEE Transactions on Electron Devices, vol. 68, pp. 3894-3900, 2021.
[90] S. Kundu, T. Shripathi, and P. Banerji, "Interface engineering with an MOCVD grown ZnO interface passivation layer for ZrO2–GaAs metal–oxide–semiconductor devices," Solid State Communications, vol. 151, pp. 1881-1884, 2011.
[91] J.K. Kim, S. Chhajed, M.F. Schubert, E.F. Schubert, A.J. Fischer, M.H. Crawford, J. Cho, H. Kim, and C. Sone, "Light-Extraction Enhancement of GaInN Light-Emitting Diodes by Graded-Refractive-Index Indium Tin Oxide Anti-Reflection Contact," Advanced Materials, vol. 20, pp. 801-804, 2008.
[92] J.K. Kim, A.N. Noemaun, F.W. Mont, D. Meyaard, E.F. Schubert, D.J. Poxson, H. Kim, C. Sone, and Y. Park, "Elimination of total internal reflection in GaInN light-emitting diodes by graded-refractive-index micropillars," Applied Physics Letters, vol. 93, pp. 221111, 2008.
[93] X. Zou, Y. Cai, W.C. Chong, and K.M. Lau, "Fabrication and Characterization of High-Voltage LEDs Using Photoresist-Filled-Trench Technique," Journal of Display Technology, vol. 12, pp. 397-401, 2016.
[94] J. Xu, W. Zhang, J. Dai, Z. Wu, Y. Fang, and C. Chen, "High performance GaN flip-chip light-emitting diodes with TiO2/SiO2 distributed Bragg reflector," International Photonics and OptoElectronics, Optica Publishing Group, Wuhan, p. JW3A.12, 2015.
[95] M. Dal Lago, M. Meneghini, N. Trivellin, G. Mura, M. Vanzi, G. Meneghesso, and E. Zanoni, "Phosphors for LED-based light sources: Thermal properties and reliability issues," Microelectronics Reliability, vol. 52, pp. 2164-2167, 2012.
[96] Y. Homma, and S. Tsunekawa, "Planar Deposition of Aluminum by RF/DC Sputtering with RF Bias," Journal of The Electrochemical Society, vol. 132, pp. 1466-1472, 1985.
[97] X. Liu, Y. Mou, Y. Peng, M. Chen, H. Wang, and R. Liang, "Light Extraction Enhancement of Deep Ultraviolet Light-Emitting Diodes by Using Aluminum Reflector Cup," 2018 19th International Conference on Electronic Packaging Technology (ICEPT), pp. 1426-1427, 2018.
[98] L. Ma, G.-D. Shen, J.-P. Liu, Z.-Y. Gao, C. Xu, and X. Wang, "Theoretical and experimental analysis of the effects of the series resistance on luminous efficacy in GaN-based light-emitting diodes," Chinese Physics B, vol. 23, pp. 118507, 2014.
[99] X. Lin, C. Zhang, S. Yang, W. Guo, Y. Zhang, Z. Yang, G. Ding, "The impact of thermal annealing on the temperature dependent resistance behavior of Pt thin films sputtered on Si and Al2O3 substrates", Thin Solid Films, vol. 685, pp. 372–378, 2019.
[100] S. Singh, A.D. Sai Nandini, S. Pal, and C. Dhanavantri, "Enhancement of light extraction efficiency of vertical LED with patterned graphene as current spreading layer," Superlattices and Microstructures, vol. 89, pp. 89-96, 2016.
[101] X. Liu, Y. Mou, Y. Peng, M. Chen, H. Wang, and R. Liang, "Light Extraction Enhancement of Deep Ultraviolet Light-Emitting Diodes by Using Aluminum Reflector Cup," International Conference on Electronic Packaging Technology (ICEPT), pp. 1426-1427, 2018.
[102] H. Huang, J. Hu, and H. Wang, "GaN-based light-emitting diodes with hybrid micro/nano-textured indium-tin-oxide layer," Journal of Semiconductors, vol. 35, pp. 084006, 2014.
[103] C. H. Liao, J. Y. Huang, C. S. Huang, and S. H. Lin, "Bandgap-Tunable Aluminum Gallium Oxide Deep-UV Photodetector Prepared by RF Sputter and Thermal Interdiffusion Alloying Method," Processes, vol.13, no. 1, pp. 68, 2025.
[104] C. C. Wang, S. H. Yuan, S. L. Ou, S. Y. Huang, K. Y. Lin, Y. A. Chen, P. W. Hsiao, and D. S. Wuu, "Growth and characterization of co-sputtered aluminum-gallium oxide thin films on sapphire substrates," Journal of Alloys and Compounds, vol. 765, pp. 894-900, 2018.
[105] A. K. Saikumar, S. D. Nehate, and K. B. Sundaram, "A review of recent developments in aluminum gallium oxide thin films and devices," Solid State and Material Sciences, vol. 47, pp. 538-569, 2022.
[106] J. Ajayan, S. Sreejith, N. A. Kumari, M. Manikanasn, S. Sen, and M. Kumar, "Amorphous indium gallium zinc oxide thin film transistors (a-IGZO-TFTs): Exciting prospects and fabrication challenges," Microelectronic Engineering, vol. 298, pp. 112327, 2025.
[107] Y. Zhu, Y. He, S. Jiang, L. Zhu, C. Chen, and Q. Wan, "Indium-gallium-zinc-oxide thin-film transistors: Materials, devices, and applications," Journal of Semiconductors, vol. 42, no. 3, pp. 031101, 2021.
[108] Y. Han, J. Seo, D. H. Lee, and H. Yoo, "IGZO-Based Electronic Device Application: Advancements in Gas Sensor, Logic Circuit, Biosensor, Neuromorphic Device, and Photodetector Technologies," Micromachines, vol.16, no. 2, pp. 118, 2025.
[109] A. Zuttel, A. Remhof, A. Borgschulte, and O. Friedrichs, “Hydrogen: the future energy carrier,” Phil. Trans. R. Soc. A, vol. 368, pp. 3329-3342, 2010.
[110] F. Martins, C. Felgueiras, and M. Smitkova, “Fossil fuel energy consumption in european countries,” Energy Procedia., vol. 153, pp. 107-111, 2018.
[111] T. M. Letcher, “1 - Introduction with a focus on atmospheric carbon dioxide and climate change,” Future Energy (Third Edition), pp. 3-17, 2020.
[112] N. Armaroli and Vincenzo Balzani, “The hydrogen issue,” Chem. Eur. J., vol. 4, pp. 21-36, 2011.
[113] C. H. Chang, T. C. Chou, W. C. Chen, J. S. Niu, K. W. Lin, S. Y. Cheng, W. C. Liu, “Study of a WO3 thin film based hydrogen gas sensor decorated with platinum nanoparticles,” Sens. Actuators B Chem., vol. 317, pp.128145, 2020.
[114] S. J. Teichner, “Recent studies in hydrogen and oxygen spillover and their impact on catalysis,” Appl. Catal., vol. 62, pp. 1-10, 1990.
[115] W. Karim, C. Spreafico, A. Kleibert, J. Gobrecht, J. V, Vondele, Y. Ekinci, and J. A. van Bokhoven, “Catalyst support effects on hydrogen spillover,” Nature, vol. 541, pp.68-71, 2017.
[116] L. Wang, S. Wang, M. Xu, X. Hu, H. Zhang, Y. Wang, and W. Huang, “A Au functionalized ZnO nanowire gas sensor for detection of benzene and toluene,” Phys. Chem. Chem. Phys., vol. 15, pp. 17179-17186, 2013.
[117] U. Roland, A. Hebestreit, A. Taoussanis, M. Eiserbeck, F. Holzer, A. Wotzka, and S. Wohlrab, “Cost-effective selective hydrogen sensor based on the combination of catalytic spillover effect and impedance measurement,” Int. J. Hydrogen Energy, vol. 48, pp. 37550-37562, 2013.
[118] R. Y. Peng and W. C. Liu, “Study of a high-performance chemoresistive ethanol gas sensor synthesized with au nanoparticles and an amorphous IGZO thin film,” IEEE Trans. Electron Devices, vol. 68, pp. 753-760, 2020.
[119] Q. Shangguan, Y. Lv, and C. Z. Jiang, “A Review of Wide Bandgap Semiconductors: Insights into SiC, IGZO, and Their Defect Characteristics,” Nanomaterials, vol. 14, no. 20, pp. 1679, 2024.
[120] P. C. Chou, H. I. Chen, I. P. Liu, C. C. Chen, J. K. Liou, K. S. Hsu, and W. C. Liu, “On the ammonia gas sensing performance of a RF sputtered NiO thin-film sensor,” IEEE Sens. J., vol. 15, pp. 3711-3715, 2015.
[121] S. K. Lee, D. Chang, and S.W. Kim, “Gas sensors based on carbon nanoflake/tin oxide composites for ammonia detection,” J. Hazard. Mater., vol. 268, pp. 110-114, 2014.
[122] R. Ab Kadir, Z. Li, A.Z. Sadek, R. Abdul Rani, A.S. Zoolfakar, M.R. Field, J.Z. Ou, A.F. Chrimes, and K. Kalantar-zadeh, “Electrospun granular hollow SnO2 nanofibers hydrogen gas sensors operating at low temperatures,” J. Phys. Chem. C, vol. 118, pp. 3129-3139, 2014.
[123] N. Yamazone, K. Suematsu, and K. Shimanoe, “Surface chemistry of neat tin oxide sensor for response to hydrogen gas in air,” Sens. Actuators B Chem., vol. 227, pp. 403-410, 2016.
[124] H. Chang, T. Chou, W. Chen, J. S. Niu, K. W. Lin, S. Y. Cheng, and W. C. Liu, “Study of a WO3 thin film based hydrogen gas sensor decorated with platinum nanoparticles,” Sens. Actuators B Chem., vol. 317, pp. 128145, 2020.
[125] A. Sutka, M. Stingaciu, G. Mezinskis, and A. Lusis, “An alternative method to modify the sensitivity of p-type NiFe2O4 gas sensor,” J. Mater. Sci., vol. 47, pp. 2856-2863, 2012.
[126] S. S. Badadhe and I. S. Mulla, “H2S gas sensitive indium-doped ZnO thin films: Preparation and characterization,” Sens. Actuators B Chem., vol. 143, pp. 164-170, 2009.
[127] L. Zhang, Q. Guo, Q. Tan, Z. Fan, and J. Xiong, “High performance amorphous IGZO thin-film transistor based on alumina ceramic,” IEEE Access., vol. 7, pp. 184312-184319, 2019.
[128] P. Cao, Z. Yang, S. T. Navale, S. Han, X. Liu, W. Liu, Y. Lu, F. J. Stadler, and D. Zhu, “Ethanol sensing behavior of Pd-nanoparticles decorated ZnO-nanorod based chemiresistive gas sensors,” Sens. Actuators B Chem., vol. 298, pp. 126850, 2019.
[129] G. B. Hoflund, and Z. F. Hazos, “Surface characterization study of Ag, AgO, and Ag2O using x-ray photoelectron spectroscopy and electron energy-loss spectroscopy,” Physical Review B, vol. 62, pp. 11126, 2000.
[130] C. C. Hsu, J. S. Niu, and W. C. Liu, “Hydrogen sensing properties of a tin dioxide thin film incorporated with evaporated palladium nanoparticles,” ECS J. Solid State Sci. Technol., vol. 11, pp. 027001, 2024.
[131] K. H. Luo, I. P. Liu, C. C. Chiu, K. W. Lin, W. C. Hsu, and W. C. Liu, “Comprehensive study of formaldehyde gas sensing performance of a GTO thin film incorporated with gold nanoparticles,” Sens. Actuators B Chem., vol. 398, pp. 134770, 2024.
[132] C. Lee and W. C. Liu, “A high-performance Pd nanoparticle (NP)/WO3 thin-film-based hydrogen sensor,” IEEE Electron Device Lett., vol. 40, pp. 1194-1197, 2019.
[133] P. S. Lin, J. S. Niu, and W. C. Lin, “Hydrogen sensing properties of an aluminum doped zinc oxide layer decorated with palladium nanoparticles,” IEEE Electron Device Lett., vol. 43, pp. 280-283, 2021.
[134] J. S. Niu, R. Y. Peng, C. C. Chiu, J. H. Tsai, W. C. Hsu, K. W. Lin, and W. C. Liu, “Comprehensive study of hydrogen gas sensing performance of an amorphous In-Al-Zn-O (a-IAZO) thin film synthesized with Pd nanoparticles,” IEEE Trans. on Electron Devices, vol. 70, pp. 4837-4842, 2023.
[135] M. Kang, and S. Kang, "Influence of Al2O3 additions on the crystallization mechanism and properties of diopside/anorthite hybrid glass-ceramics for LED packaging materials," Journal of Crystal Growth, vol. 326, pp. 124-127, 2011.
[136] M. Kang, and S. Kang, "Effects of Al2O3 addition on physical properties of diopside based glass–ceramics for LED packages," Ceramics International, vol. 38, pp. S551-S555, 2012.
[137] L. Chen, X. He, Y. Liang, Y. Sun, Z. Zhao, and J. Hu, “Synthesis and gas sensing properties of palladium-doped indium oxide microstructures for enhanced hydrogen detection,” J. Mater. Sci. Mater. Electron., vol. 27, pp. 11331-11338, 2016.
[138] O. Lupan, V. Postica, N. Ababii, M. Hoppe, V. Cretu, I. Tiginyanu, V. Sontea, T. Pauport´e, B. Viana, and R. Adelung, “Influence of CuO nanostructures morphology on hydrogen gas sensing performances,” Microelectron. Eng., vol. 164, pp. 63-70, 2016.
[139] N. V. Toan, N. V. Chien, N. V. Duy, H. S. Hong, H. Nguyen, N. D. Hoa, and N. V. Hieu, “Fabrication of highly sensitive and selective H2 gas sensor based on SnO2 thin film sensitized with microsized Pd islands,” J. Hazard. Mater., vol. 301, pp. 433-422, 2016.
[140] S. M. Mohammad, Z. Hassan, R. A. Talib, N. M. Ahmed, M. A. Al-Azawi, N. M. AbdAlghafour, C.W. Chin, and N. H. Al-Hardan, “Fabrication of a highly flexible low cost H2 gas sensor using ZnO nanorods grown on an ultra-thin nylon substrate,” J. Mater. Sci.: Mater. Electron., vol. 27, pp. 9461-9469, 2016.
[141] T. T. L. Dang, M. Tonezzer, and V. H. Nguyen, “Hydrothermal growth and hydrogen selective sensing of nickel oxide nanowires,” J. Nanomater., vol. 2015, pp. 785856, 2015.
[142] E. Amani and K. Khojier, “Improving the hydrogen gas sensitivity of WO3 thin films by modifying the deposition angle and thickness of different promoter layers,” Int. J. Hydrog. Energy, vol. 42, pp. 29620-29628, 2017.
[143] N. Pradeep, C. Venkatachalaiah, U. Venkatraman, C. Santhosh, A. Bhatnagar, S. K. Jeong, and A.N. Grace, “Magnesium oxide nanocubes deposited on an overhead projector sheet: synthesis and resistivity-based hydrogen sensing capability,” Microchim. Acta, vol. 184, pp. 3349-3355, 2017.
[144] Y. C. Yang, J.S. Niu, and W.C. Liu, “Study of a palladium nanoparticle/indium oxide-based hydrogen gas sensor,” IEEE Trans. Electron Devices., vol. 69, pp. 318-324, 2021.
[145] X. Luo, K. You, Y. Hu, S. Yang, X. Pan, Z. Wang, W. Chen, and H. Gu, “Rapid hydrogen sensing response and aging of α-MoO3 nanowires paper sensor,” Int. J. Hydrog. Energy., vol. 42, pp. 8399-8405, 2017.