本論文主要是成長並研製高亮效率之三族氮化物光電元件。本研究主要提出二個方向來提升氮化鎵發光二極體的效率，其中包含，應用氮化鋁鎵和氮化銦鎵組成的超晶格結構於電子阻檔層中。以數位切換氮化銦和氮化鎵的方式，成長氮化銦鎵量子井結構。另外在氮化銦鎵太陽能電池中，提出兩種方法提升轉換效率，為利用濺鍍法成長的氮化鋁成核層，和n型氮化鋁鎵量子井障。
首先利用鎂摻雜的氮化鋁鎵和氮化銦鎵組成的超晶格結構於電子阻檔層中，能夠改善氮化鎵發光二極體的操作電壓、光輸出功率、效率下降的效應。在超晶格電子阻檔層中，較厚的氮化銦鎵能夠提高電子的位障，降低電洞的位障並防止電子漏電流進入p型區中，也加強了電洞的注入效率。同時擁有較低的側向電阻，於大電流操作下有較佳的電流散佈能力。
其次以數位切換氮化銦和氮化鎵的方式成長高品質且厚的氮化銦鎵量子井結構。其量子井在銦含量17.6%，厚度達7奈米下同時可保有高晶格品質。在操作電流60 mA下，和傳統的量子井比較，其光輸出功率至少改28.9%。但是其效率下降的效應比起傳統的量子井較為嚴重。其光學特性上是優於傳統的量子井。利用變溫光激發光強度得到的活化能和。以數位切換氮化銦和氮化鎵的方式成長的厚量子井其活化能48 meV 高於傳統薄量子井25 meV 。此外其sigma值為19 meV 小於傳統薄量子井的sigma值25 meV 。
接著利用濺鍍法成長的氮化鋁成核層於氮化銦鎵太陽能電池中。利用濺鍍法成長的氮化鋁成核層可有效地降低磊晶材料的混合型差排。使得復合電流降低和減少漏電流路徑，因此其短路電流和開路電壓都獲得改善。其1-sun η為1.92%改善27.2%比起傳統的氮化鎵成核層為1.51%。此外在聚光100-sun 下其η為1.99%改善18.5%比起傳統的氮化鎵成核層為1.68%。
最後為利用兩對氮化鋁鎵/氮化銦鎵量子井取代氮化鎵/氮化銦鎵量子井結構，能夠改善氮化銦鎵太陽能電池的開路電壓、填充因子、轉換效率。其在2 V下於365 nm到420 nm的外部量子效率大於傳統氮化鎵/氮化銦鎵量子井。透過模擬分析為利用兩對氮化鋁鎵/氮化銦鎵量子井於接近開路電壓下，能夠降低復合電流。。因此其填充因子獲得改善，並使得其1-sun η為1.86%改善27.4%比起傳統的n型氮化鎵量子井障為1.46%。

Growth and fabrication of high efficiency GaN-based optoelectronic devices were successfully demonstrated in this dissertation. This dissertation proposed two directions to enhance the efficiency for fabrication of InGaN-based LEDs, include the methods of Mg-doped AlGaN/InGaN superlattice electron blocking layer and digital InN/GaN growth in InGaN well. We also proposed two methods to improve the efficiency of InGaN-based solar cells by introducing ex-situ AlN nucleation layer and Si-doped AlGaN barriers.
Firstly, the operating voltage, light output power, and efficiency droops of GaN-based light emitting diodes (LEDs) were improved by introducing Mg-doped AlGaN/InGaN superlattice (SL) electron blocking layer (EBL). The thicker InGaN layers of AlGaN/InGaN SL EBL could have a larger effective electron potential height and lower effective hole potential height than that of AlGaN EBL. This thicker InGaN layer could prevent electron leakage into the p-region of LEDs and improve hole injection efficiency to achieve a higher light output power and less efficiency droops with the injection current. The low lateral resistivity of Mg-doped AlGaN/InGaN SL would have superior current spreading at high current injection.
Secondly, thick InGaN wells of LEDs with high crystal quality can be prepared by using digital InN/GaN growth for the InGaN wells. The thickness of high crystal quality InGaN wells can be sustained with In% of 17.6% more than 7 nm. The 60 mA output power of LEDs with thick InN/GaN alternative growth InGaN wells indicate an enhancement of at least 28.9% compared with that of LEDs with conventional InGaN wells. However, LEDs with thick InN/GaN alternative growth InGaN wells have larger efficiency droops than LEDs with conventional InGaN wells. Compared with conventionally grown thin InGaN wells, thick InGaN wells with digitally grown InN/GaN exhibit superior optical properties. The activation energy (48 meV) of thick InGaN wells (generated by digital InN/GaN growth from temperature-dependent integrated photoluminescence intensity) is larger than the activation energy (25 meV) of conventionally grown thin InGaN wells. Moreover, thick InGaN wells with digitally grown InN/GaN exhibit a smaller  value (the degree of localization effects) of 19 meV than that of conventionally grown thin InGaN wells (23 meV).
Thirdly, GaN solar cells (SCs) with ex-situ AlN nucleation layer are examined in this study. GaN with sputtered ex-situ AlN nucleation layer has mixed-type dislocation density at approximately one order less than that of GaN with in-situ GaN nucleation layer. The reduction of dislocation density by the sputtered AlN nucleation layer could suppress the reverse leakage current and the recombination forward current in low forward voltage range of SCs, and then can increase Jsc and Voc of the SCs. 1-sun η% of SCs with ex-situ AlN nucleation (1.92%) showed an enhancement of 27.2% compared with that of conventional SC at 1.51%. Furthermore, the 100-sun η% of SCs with ex-situ AlN nucleation (1.99%) showed 18.5% improvement compared with that of conventional SC (1.68%).
Finnaly, the Voc, FF%, and η% of GaN-based SCs can be improved by replacing an initial 2-pair GaN/InGaN with 2-pair AlGaN/InGaN multilayer. The IPCE of SCs with 2-pair AlGaN/InGaN multilayer is higher than that with GaN/InGaN at 2 V for wavelengths in range of 365 nm to 420 nm. From the results of the numerical simulation, we found that the FF% improvement of the SCs with the 2-pair AlGaN/InGaN multilayer should be attributed to the photo-generated carrier recombination rate suppression near the bias of the Voc. The 1-sun η of SCs with Si-doped Al0.10GaN barriers (1.86%) showed 27.4% enhancement compared with that with Si-doped GaN barriers (1.46%).

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