臺灣博碩士論文加值系統

本論文研究藉由調變發光二極體(Light-Emitting Diode, LED)量子井(multiple quantum well)中銦(In)的組成比，實現不同的波長，分別為520、450、420、390和370nm，五種發光二極體的主動區之量子井(Well)與位障(Barrier)層，分別為GaN/In0.39Ga0.61N、GaN/In0.24Ga0.76N、GaN/In0.17Ga0.83N、AlGaN/In0.08Ga0.92N與AlGaN/In0.02Ga0.98N，並命名為VG、VB、VV、VU和VD，分別探討其光電特性、溫度特性與響應特性。
在光電特性部分，分別量測五批樣品的光輸出功率和外部量子效率，發現VG的輸出功率與量子效率皆很差，推測原因為其銦組成比例最高，銦聚集(In-rich cluster)的情形最嚴重，形成較多的侷限能態(Localization state)，當電流增加時會使歐傑復合(Auger recombination)的機率增加，因此外部量子效率衰減最嚴重。而VU和VD的效率衰減一樣很嚴重，我們認為影響載子的溢流部分主要是因為能障較低，電子傳輸時跨越能障逃脫至主動區外，導致效率的衰減。
在溫度效應的量測部分，主要分析五批樣品在高溫時對於溫度的依賴性，當環境溫度升高後，載子會因為溫度而獲得額外能量後逃脫量子井，發現侷限能態較多的樣品可以有效的抑制載子的溢流。另外，在低溫環境下可以透過光強度的變化觀察五種批品不同主動區內的載子傳輸情形；從波長的變化也可以觀察到五批樣品的侷限能態情形。
在頻率響應的部分，主要分析五批樣品隨著頻率的上升decay的情形，可發現VG的衰減情形最嚴重，推測原因為VG銦含量最高，有最多的侷限能態(Localization state)，使的歐傑復合的情形嚴重，因此最快decay。

n this study, nitride-based green, blue, and ultraviolet light-emitting diodes (LEDs) were fabricated and investigated. The emission wavelength of VG, VB, VV, VU, and VD of the LEDs are 520, 450, 420, 390, and 370 nm, respectively. Then, the optical, temperture-dependence and response properties of the LEDs will be discussed.
We analyze the light output power (LOP), external quantum efficiency (EQE), and normalized EQE of the LEDs for five samples , respectively. VB and VV exhibit better LOPs and EQEs, which can be attributed to carrier localization state effect induced by In-rich cluster. However, the LOPs and EQEs of VG, VU, and VD are lower due to stronger non-radiative recombination effect generated by higher defect density. And we can be seen clearly that VG has the worst efficiency droop. It is because the efficiency droop behavior of VG with highest indium composition of quamtum wells is the most severe due to the strongest delocalization phenomenon at high current density.
We analyze the temperature effect for three samples at high and low temperature, respectively. When the ambient temperature rises, the carrier will escape from the quantum wells after gaining additional energy by the temperature, and it is found that the sample with more localization state can effectively suppress the carrier overflow. In addition, the low ambient temperature can observe through the light intensity of this three different active regions of the carrier transport situation. The localization state of the three samples can also be observed from the variation of wavelength.
And we analyze the frequency response of the LEDs. It was found that VG has the lowest 3-dB frequency. The RC time constant and the spontaneous recombination time are two major speed limiting factors. The RC time constants of these five LEDs are almost the same analyzed by C-V and I-V characteriatics. Therefore, VG with the lowest 3-dB
v
frequency can be attributed to the strongest delocalization phenomenon at high current density.

摘 要 ....................................................................................................................... III
ABSTRACT ................................................................................................................. IV
誌 謝 ....................................................................................................................... VI
圖目錄 .......................................................................................................................... X
第一章 序論 .................................................................................................................. 1
1.1 發光二極體背景介紹 ............................................................................................ 1
1.2 研究動機 ................................................................................................................ 2
1.3 整體架構 .............................................................................................................. 12
參考文獻 .................................................................................................................... 13
第二章 基礎理論與元件製作 .................................................................................... 16
2.1 氮化鎵系列材料特性介紹 .................................................................................. 16
2.2 氮化鎵發光二極體之發光原理 .......................................................................... 18
2.3 應力與極化效應 .................................................................................................. 22
2.4 侷限能態 .............................................................................................................. 24
2.5發光效率及類別介紹 .......................................................................................... 25
(一)內部量子效率(Internal Quantum Efficiency，IQE) ....................................... 25
(二)光取出效率(Light Extraction Efficiency，LEE) ......................................... 26
(三)外部量子效率(External Quantum Efficiency，EQE) ................................. 26
(四) 功率轉換效率 (Power Efficiency) ............................................................. 27
2.6 效率下滑之因素 .................................................................................................. 27
(一) 極化效應 .................................................................................................... 27
(二) 電子溢流 .................................................................................................... 29
(三) 電洞注入效率 ............................................................................................ 29
(四) 歐傑複合 .................................................................................................... 31
(五) 磊晶品質 .................................................................................................... 33
(六) 熱效應 ........................................................................................................ 37
(七) 銦原子的群聚效應 ................................................................................... 40
2.7 實驗樣品架構 ...................................................................................................... 41
參考文獻 .................................................................................................................... 42
第三章 光電特性量測與分析 .................................................................................... 46
3.1 電特性量測與分析 .............................................................................................. 46
3.2 光特性量測與分析 .............................................................................................. 47
3.2.1 電流-光輸出功率量測與分析 ..................................................................... 47
3.2.2 外部量子效率與衰減 .................................................................................. 48
3.2.3 半高寬 .......................................................................................................... 52
第四章 溫度效應之電致發光量測與分析 ................................................................ 55
4.1 高溫之電致發光量測與分析 .............................................................................. 55
4.1.1 溫度-電壓特性量測與分析 ......................................................................... 55
4.1.2 溫度-光功率特性量測與分析 ..................................................................... 57
4.2 低溫之電致發光量測與分析 .............................................................................. 60
4.2.1 溫度-電壓特性量測與分析 ......................................................................... 60
4.2.2 溫度-光強度特性量測與分析 ..................................................................... 64
4.2.3 波長變化 ...................................................................................................... 67
參考文獻 .................................................................................................................... 71
第五章 TREL量測與分析........................................................................................... 72
5.1頻率響應量測與分析 .......................................................................................... 73
第六章、結論與展望 .................................................................................................... 75
6.1結論 ...................................................................................................................... 75
6.2未來展望 .............................................................................................................. 76

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