本論文主要是針對氮化鎵發光二極體在發光效率以及抗靜電保護能力上做探討。
我們透過製程和磊晶兩種方式去提升發光二極體的電流散佈能力。磊晶部分我們是在主動區與N型氮化鎵之間插入輕摻雜N型氮化鎵磊晶層。製程部分則是利用不同電流阻障層的製作方法和改變P型延伸電極厚度兩方面來探討。從量測結果可以發現發光效率最高能有效提升47 %，並且從發光強度分布量測實驗上也可以清楚觀察到電流散佈有所改變。雖然從製程方式亦能增強光特性，但是抗靜電保護能力卻無法相對提升。
接著，我們利用在主動層量子位障中摻雜矽以及改變未摻雜氮化鎵磊晶層厚度來觀察主動區量子侷限史塔克效應的變化。從量測結果發現在主動層量子位障中摻雜矽並不會對量子井中的量子史塔克效應產生影響。而在改變未摻雜氮化鎵磊晶層厚度的實驗中，我們發現元件內部電容值會隨厚度增加而漸少，亦因此降低抗靜電保護能力。一般而言，元件漏電過大會降低電容值，但是在此研究中並非如此。因此我們認為是自發極化場影響相同電場方向的內建電場，使得空乏區寬度受影響進而改變電容值。
最後，我們利用不同應力釋放層以及不同量子位障厚度來探討量子井中壓電極化的影響。從光學量測實驗中得知，當量子井內壓電極化較大時，元件發光波長偏向長波長，且在波長對電流圖中其因屏蔽效應所造成的藍移量也相對較多。我們利用變溫電致發光量測來探討不同壓電極化的差異。從此實驗中，我們發現隨著溫度升高，壓電極化較強的元件其藍移轉紅移的相對電流值會愈來愈大。主要是因為溫度的升高可以提供載子額外能量使其容易逃脫主動區，導致量子井中的屏蔽效應需要更大的電流注入來完成。藉由此量測手法我們可以初估元件的壓電極化大小。

In this dissertation, the luminous efficiency and electrostatic discharge protection ability on GaN-based light emitting diodes (LEDs) were investigated and fabricated.
We can enhance the current spreading ability on LEDs using epitaxial and process technologies. In epitaxial design, we inserted a light-doping n-GaN layer between active region and n-GaN layer. In process design, we used different ways to fabricate the current blocking layer and modulated p-extension electrode thickness. The light output power measured from the LEDs with best current spreading ability is 47 % larger than that of conventional LEDs. In contrast, light output power is much more uniform across the whole chip. Although the optical property can be improved by process technology, the electrostatic discharge (ESD) cannot be enhanced oppositely.
In second section, we observed the quantum-confined stark effect (QCSE) within the active region by doping Si atom in quantum barriers and modulated the un-doped GaN layer thickness. During the optical experiment, it is found that doping Si atom in quantum barriers cannot affect the QCSE in each quantum well. But, the internal capacitance value decreased as increasing the un-doped GaN layer thickness. Thus, the ESD protection ability decayed. In general, the LED with large leakage will result in low internal capacitance. Therefore, we consider that the variation of internal capacitance could be attributed to an increase in built-in electric field induced by stronger spontaneous polarization field.
Finally, we investigated the piezoelectric polarization field within each quantum well using different pre-strain interlayer and different quantum barrier thickness. According to the results, the LED with strong piezoelectric polarization field will emit long wavelength. In emission wavelength as a function of injection current characteristic, the strong piezoelectric polarization field also results in severe blue-shift. In order to differentiate the piezoelectric polarization field for the fabricated LEDs, the temperature-dependent EL characteristics were measured and achieved. It is worthy noted that the value of injection current, at which the wavelength of blue-shift changed to red-shift, shifted to larger injection current when the temperature increased. This is because that the carriers would be excited by the higher ambient temperature. Thus, it would escape from the MQWs, and the energy band-gap of MQW caused by QCSE cannot be screened and filled effectively. In other words, it needs higher injection current to provide more carriers which can complete the screening of QCSE of LEDs.

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Chapter2
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Chapter3
[1] C. C. Liu, Y. H. Chen, M. P. Houng, Y. H. Wang, Y. K. Su, W. B. Chen, and S. M. Chen, “Improved light-output power of GaN leds by selective region activation,” IEEE Photonics Technol. Lett., vol. 16, p. 1444-1446, 2004.
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Chapter4
[1] S. J. Chang, C. F. Shen, W. S. Chen, T. K. Ko, C. T. Kuo, K. H. Yu, S. C. Shei, and Y. Z. Chiou, “Nitride-based LEDs with an insulating SiO2 layer underneath p-pad electrodes,” Electrochem. Solid State Lett., vol. 10, p. H175-H177, 2007.
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Chapter5
[1] Z. Zheng, Z. Chen, Y. Xian et al., “Enhanced electrostatic discharge properties of nitride-based light-emitting diodes with inserting Si-delta-doped layers,” Appl. Phys. Lett., vol. 99, p. 111109, 2011.
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Chapter6
[1] Z. H. Zhang, S. T. Tan, Z. Ju, W. Liu, Y. Ji, Z. Kyaw, Y. Dikme,X. W. Sun,and H. Volkan, "On the Effect of Step-Doped Quantum Barriers inInGaN/GaN Light Emitting Diodes," J. Disp. Technol., vol. 9, pp. 226-233, 2013.
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Chapter7
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