在白光發光二極體照明的應用上，需以大面積發光二極體提高輸出功率並且能有效提升轉換效率，達到節能、環保、低成本的高功率固態照明。但大面積發光二極體隨著高電流注入時，因 N 型氮化鎵半導體的電阻率大都大於 P 型透明導電層，所以會增加 N 型電極附近電流擁塞的情況，而造成元件局部熱累積並使得量子效率急速下降，本論文提供一雙異質接面“氮化鋁鎵/氮化鎵/氮化銦鎵”電子流散佈層，並利用此結構改善發光二極體尺寸大型化時出現之電流擁塞現象，並且對於結構模擬與光電特性有深入的研究與探討。
本論文在光電特性探討方面，與傳統發光二極體相較之下，具單異質接面“氮化鋁鎵/氮化鎵”結構、雙異質接面“氮化鋁鎵/氮化鎵/氮化銦鎵”結構發光二極體的光強度改善，依序增強至 (在350 mA下) 93.7 mW、105.6 mW、115.2 mW。另一方面，由於在不同的異質結構上成長的量子井可能會受到應力的變化而改變量子井中的壓電效應，所以吾人以倒晶格向量空間量測具異質結構之量子井，觀察量子井的晶格應力變化，並配合量子井的光激發光波長定性極化分析，證明量子井受到極化效應卻不影響光輸出功率；並由量測得知光影像變異度依序降低至 (Ref @ 500 mA) 31.5 %、24.3 %、21.4 %，與高電流注入量測發光二極體的接面溫度依序降低為 (Ref @ 350 mA) 132.8 oC、120.1 oC、113.4 oC，可增加商業上元件使用的熱穩定性。

In the application of white-light LED illumination, a bigger illuminating area is needed to increase output power and effectively raise conversion efficiency, further to achieve a high-power solid state lighting that can meet the requirements of energy saving, environment protection and low cost. However, the fact that the resistivity of N-type GaN semiconductor is greater than that of P-type transparent conducting layer can lead to current congestion around N-type electrode and result in local heat accumulation, which will drastically reduce quantum efficiency. In this study, a current spreading layer of dual- herterojunction (AlGaN/GaN/InGaN) was presented to improve the situation of current congestion when a LED of increased size is used. Additionally, a deeper exploration was conducted on structure simulation and photoelectric properties.
In terms of the exploration of the photoelectric properties of LED with current spreading layer, comparison was made between luminous intensities of traditional GaN LED and LEDs with current spreading layer of heterojunctions of AlGaN/GaN and AlGaN/GaN/InGaN structures. The results showed that the luminous intensities of LED with current spreading layer of AlGaN/GaN and AlGaN/GaN/InGaN structures could be improved to 93.7 mW、105.6 mW、115.2 mW when 350mA is applied. On the other hand, due to piezoelectric polarization''s possible influence on the quantum confined stark effect of multi-quantum well, multi-quantum well with hetero-structure was measured using reciprocal lattice vector space to observe its stress change. Moreover, a qualitative polarization analysis was conducted on the wavelength of the excited light emitted from multi-quantum well to prove the effect of quantum well polarization won''t be affected by the output power of light. The measurements suggested that the light image uniformity variations were reduced to 31.5 %、24.3 %、21.4 % (Ref @ 500 mA) respectively and the temperatures measured when high current was applied were respectively lowered to 132.8 oC、120.1 oC、113.4 oC (Ref @ 350 mA), which proved that LED with current spreading layer presented in this study can improve the element''s heat stability for commercial use.

[1] B. Damilano, et al. “Monolithic white light emitting diodes using a (Ga,In)N/GaN multiple quantum well light converter”, Appl. Phys. Lett., Vol. 93, 101117 (2008).
[2] S. N. Lee, et al. “Monolithic InGaN-based white light-emitting diodes with blue, green, and amber emissions”, Appl. Phys. Lett., Vol. 92, 081107 (2008).
[3] G. Chen, et al. “Performance of high-power III-nitride light emitting diodes”, phys. stat. sol. (a) Vol. 205, pp. 1086-1092 (2008)
[4] M. R. Krames, et al. “High-brightness A1GaInN light-emitting diodes”, Proc. SPIE, Vol. 3938, pp. 2-12 (2000)
[5] Chul Huh, et al. “Improved light-output and electrical performance of InGaN-based light-emitting diode by micro roughening of the p-GaN surface”, J. Appl. Phys., Vol. 93, pp. 9383-9385 (2003)
[6] T. Fujii, et al. “Increase in the extraction efficiency of GaN-based light-emitting diodesvia surface roughening”, Appl. Phys. Lett., Vol. 84, pp. 855-857 (2004)
[7] M. R. Krames, et al. “High-power truncated-inverted-pyramid (AlxGa1-x) 0.5In0.5P/GaP light-emitting diodes exhibiting > 50% external quantum efficiency”, Appl. Phys. Lett., Vol. 75, pp. 2365-2367 (1999)
[8] S. J. Lee, S. W. Song, “Efficiency improvement in 1ightemitting diodes based on geometrically deformed chips”, Proc. SPIE, Vol. 3621, pp. 237-248 (1999)
[9] J. J. Wierer, et al. “High-power AlGaInN flip-chip light-emitting diodes”, Appl. Phys. Lett., Vol. 78, pp. 3379-3381 (2001)
[10] X. Guo, Y.L. Li, and E. F. Schubert, “Efficiency of GaN/InGaN light-emitting diodes with interdigitated mesa geometry”, Appl. Phys. Lett., Vol. 79, pp. 1936-1938 (2001)
[11] Arpan Chakraborty, et al. “Interdigitated multipixel arrays for the fabrication of high-power light-emitting diodes with very low series resistances”, Appl. Phys. Lett., Vol. 88, 181120 (2006)
[12] Z. Gong, et al. “Matrix-Addressable Micropixellated InGaN Light-Emitting Diodes With Uniform Emission and Increased Light Output”, IEEE Trans. Electron. Devices., Vol. 54, pp. 2650-2658 (2007)
[13] Chul Huh, et al. “Current blocking layer in GaN light-emitting diode”, Proc. SPIE, Vol. 4445, pp. 165-171 (2001)
[14] Chul Huh, et al. “Improvement in light-output efficiency of InGaN/GaN multiple-quantum well light-emitting diodes by current blocking layer”, J. Appl. Phys., Vol. 92, pp. 2248-2250 (2002)
[15] C. Liu, et al. “Improved Light-Output Power of GaN LEDs by Selective Region Activation”, IEEE Photon. Tech. Lett., Vol. 16, pp. 1444-1446 (2004)
[16] H. Kim, Seong-Ju Park, and Hyunsang Hwang, “Lateral current transport path, a model for GaN-based light-emitting diodes: Applications to practical device designs”, Appl. Phys. Lett., Vol. 81, pp. 1326-1328 (2002)
[17] C. H. Chen, “InGaN/GaN blue light emitting diodes with modulation-doped AlGaN/GaN heterostructure layers”, J. Vac. Sci. Technol. (A) Vol. 24, pp. 1001-1004 (2006)
[18] J. K. Sheu, G. C. Chi, and M. J. Jou, “Enhanced Output Power in an InGaN–GaN Multiquantum-Well Light-Emitting Diode With an InGaN Current-Spreading Layer”, IEEE Photon. Tech. Lett., Vol. 13, pp. 1164-1166 (2001)
[19] Y. T. Rebane, et al. “Light Emitting Diode with Charge Asymmetric Resonance Tunneling”, phys. stat. sol. (a) Vol. 180, pp. 121-126 (2000)
[20] I. Eliashevich, et al. “InGaN blue light-emitting diodes with optimized n-GaN layer”, Proc. SPIE, Vol. 3621, pp. 28-36 (1999)
[21] I. Vurgaftman and J. R. Meyer, “Band parameters for nitrogen-containing semiconductors”, J. Appl. Phys., Vol. 94, pp. 3675-3696 (2003)
[22] O. Ambacher, et al. “Pyroelectric properties of Al(In)GaN GaN hetero- and quantum well structures”, J. Phys. Condens. Matter., Vol. 14, pp. 3399-3434 (2002)
[23] Properties Editor Default Parameters”, STR, Inc. 2008
[24] W. B. JOYCE, S. H. WEMPLE, “Steady-State Junction-Current Distributions in Thin Resistive Films on Semiconductor Junctions (Solutions of ▽2V = ±eV)”, J. Appl. Phys., Vol. 41, pp. 3818-3830 (1970)
[25] H. Kim, et al. “Measurements of current spreading length and design of GaN-based light emitting diodes”, Appl. Phys. Lett., Vol. 90, 063510 (2007)
[26] X. Guo and E. F. Schubert, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates”, Appl. Phys. Lett., Vol. 78, pp. 3337-3339 (2001)
[27] 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)
[28] H. Kim, et al. “Modeling of a GaN-based light-emitting diode for uniform current spreading”, Appl. Phys. Lett., Vol. 77, pp. 1903-1904 (2000)
[29] H. Kim, S.-J. Park, and H. Hwang, “Lateral current transport path, a model for GaN-based light-emitting diodes: Applications to practical device designs”, Appl. Phys. Lett., Vol. 81, pp. 1326-1328 (2002)
[30] Y. Xi and E. F. Schubert, “Junction–temperature measurement in GaN ultraviolet light-emitting diodes using diode forward voltage method”, Appl. Phys. Lett., Vol. 85,pp. 2163-2165 (2004)
[31] R. Czernecki, et al. “Strain-compensated AlGaN/GaN/InGaN cladding layers in homoepitaxial nitride devices”, Appl. Phys. Lett., Vol. 91, 231914 (2007)