臺灣博碩士論文加值系統

本論文將介紹主要的磷化鋁銦鎵發光二極體元件結構，其中包含了具有吸光基板的AS發光二極體、透明基板的TS發光二極體和採用晶體內部全反射層的ODR發光二極體。
AS發光二極體的基板材料為砷化鎵，砷化鎵是一不透明且會吸收光線的材料，因此TS發光二極體以一個12mil(304.8μm × 304.8μm)面積大小的發光二極體來說，其亮度僅有100mcd，而且散熱不佳的特性是另一個AS發光二極體的缺點；近年來許多研究克服了這些缺點，TS發光二極體就是此類的產品，它將原本吸光且散熱不佳的砷化鎵基板移除掉，選擇藍寶石作為其基板的材料，因為藍寶石是一種透明的材料，光線不會完全被吸收，在本文的實驗中發現，在一個面積為14mil(355.6μm × 355.6μm)大小的發光二極體，TS發光二極體的最大亮度可以達到250mcd。
但是TS發光二極體有一個最大的缺點，那就是藍寶石基板的熱傳導係數不佳，大約是35W/(m K)；在本文中我們採用矽來當作新式ODR發光二極體的基板，因為矽材料有較佳的熱傳導係數，大約是151 W/(m K)；使用矽基板，ODR發光二極體可迅速的將多重量子井工作區，因發光所產生的熱傳導至外界，因散熱佳的特性，ODR發光二極體比起AS和TS來說，可以承受更大的驅動電流。因為矽基板並非透明，所以我們使用電子槍蒸鍍系統在磷化鎵表面進行銀反射鏡、鉑擴散阻擋層和氧化銦錫電流擴散層的蒸鍍，而形成一複合的反射層；因為有此一新型態的製程方法，ODR光發二極體的亮度跟TS發光二極體比較，有接近40%的效率提升，並且達到350mcd，而其在順向電流20mA的點測下，順向電壓為2.1V；可靠度測試的結果也顯示，在順向電流從0mA增加到100mA的情況下，發光波長的變化量可小於1nm；這些測試數據顯示，ODR發光二極體比其他結構的發光二極體更適合應用於高功率的發光二極體製程應用上。

In the thesis, the major classes of AlGaInP device structures, including AS (absorbing-substrate) LEDs, TS (transparent substrate) LEDs, and LEDs using omni-directional reflectors (ODRs) are introduced.

For the GaAs-based AS LED the significant fraction of light is absorbed in the GaAs substrate. This results in a luminous intensity as low as 100mcd for a 12mil (304.8μm × 304.8μm) chip size LED. Meanwhile, bad thermal stable characteristic is another shortcoming for AS LEDs. More recent developments such as TS LEDs can avoid the drawbacks. TS LEDs removes the AS LEDs GaAs substrate and chooses sapphire as the substrate. Because of the transparent sapphire, light won’t be absorbed by the substrate. In this work a maximum luminous intensity up to 250mcd for a 14mil (355.6μm × 355.6μm) chip size LED is achieved in TS LED.

However, the low thermal conductivity of about 35W/(m K) for sapphire substrate in TS LED is still an important drawback. In this work, we use Si as the ODR LEDs substrate. The Si thermal conductivity is about 151 W/(m K). Higher thermal conductivity of Si substrate allows lower active region temperatures and thus higher drive currents as compared to the sapphire or GaAs is achieved. Because of Si substrate isn’t transparent, we use E-Gun evaporation system to evaporate Ag metal reflector, Pt barrier layer and ITO current spreading layer on GaP surface to be a hybrid reflective layer. According to this new process method the ODR LEDs luminous intensity will be greatly enhanced 40% to about 350 mcd than TS LEDs. Meanwhile, the forward voltage is about 2.1 V at a forward current of 20 mA. The reliability test also shows that when the forward current varied from 20mA to 100mA, the wavelength only shifts smaller than 1 nm. This shows that the new ODR LEDs is competitive in high brightness LED products.

Abstract (Chinese)
Abstract (English)

Chapter1:Introduction 1

Chapter 2: AlGaInP LED Structure Evolution and Challenge 4
2-1 Typical Long Wavelength AlGaInP LED 4
2-1-1 AS (Absorbing Substrate) LED 4
2-1-2 TS (Transparent Substrate) LED 5
2-1-3 ODR (Omni-directional reflector) LED 6
2-2 The Principle of LED 8
2-2-1 Light radiation 8
2-2-2 p-n junction 9
2-2-3 LED principle of action 10
2-3 Why choose AlGaInP material for high-efficiency LED? 11
2-4 AlGaInP LED Performance Issues: Red Shift 12
2-5 Diffusion Barrier Layer 13

Chapter 3: Equipment Introduction and ODR Fabrication 14
3-1 AlGaInP LED Process Equipment Introduction 14
3-1-1 Aligner 14
3-1-2 Wafer Bonding System 14
3-1-3 ICP 16
3-1-3 PECVD 16
3-1-4 E-Gun Evaporation System 16
3-2 ODR LED Fabrication 18
3-2-1 Sample Preparation 18
3-2-2 P-metal Ohmic Contact Leayer 18
3-2-3 Reflective Layer Evaporated Deposition 19
3-2-4 Wafer Bonding 19
3-2-5 Substrate Remove 20
3-2-6 N-metal Ohmic Contact Layer 20
3-2-7 ITO Current Spreading Layer 21
3-2-8 Mesa and Scribe Line Etching 21
3-2-9 Passivation Layer 21
3-2-10 P, N PAD Evaporated Deposition 22

Chapter 4: Experiment Results 23
4-1 Choose an Ultimate Mask for ODR LED 23
4-2 High Reflective Layer Development Results 24
4-2-1 Metal Reflective Layer 24
4-2-2 Hybrid Reflective Layer 25
4-2-3 Using a Diffusion Barrier Metal 27
4-3 The New ODR LED Performance 29
4-3-1 The WAT Data 29
4-3-2 The Chip Probe (CP) Data 30
4-3-3 E Company AS, TS LED versus ODR LED 30
for I-λ Curve
4-3-4 E Company TS LED versus ODR LED for Iv 30
4-3-5 E Company TS LED versus ODR LED for Vf 31
4-3-6 The B Company reflective type LED versus 31
ODR

Chapter 5: Conclusion and Future Works 32
References 33
Figures 37

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