通過非輻射能量轉移技術提高色彩轉換達成新穎混合型微發光二極體

Novel Hybrid Micro Light-Emitting Diodes with Increasing Color-Conversion Technical by Non-Radiative Energy Transfer

廖鎮佑(Zhen-You Liao)

指導教授 ： 郭浩中 ； 高宗聖

國立交通大學/電機學院/光電工程系所/碩士(2018年)

摘要

近年來， 微型發光二極體(micro-LEDs) 的發展主要應用在顯示器上，其設計是將發光二極體製程上的改變，包括微小化、陣列化及薄膜化。製程上，單顆 LEDs 元件尺寸大小僅在1~30 μm 等級左右。在發光二極體元件製程中，必經的蝕刻過程所產生的表面損傷將產生缺陷，這些表面缺陷會捕捉住載子而使電子電洞對復合的機率降低，進而導致 LEDs 元件發光效率削弱，而隨著元件的微米化，其缺陷對於元件的影響將更加明顯。本實驗製程內容主要是利用奈米球微影技術在LEDs 上大面積製造出奈米環結構，並利用非輻射能量轉移並結合量子點提升色彩轉換效率，製造出混合型量子點奈米環微型LEDs。其中會探討採用原子層沉積方式進行鈍化層沉積的實驗及量子井和量子點間非輻射能量轉移的機制而提高色彩轉換的研究，並可望未來將可運用於微型顯示器上。
第一章的內容包含闡述發光二極體的優點、發光二極體的應用及三族氮化物(III-Nitride materials)的優點，並簡單介紹本實驗的動機。
第二章主要為陳述研究中發光二極體與量子點材料的相關原理與介紹，並論述非輻射能量轉移運動機制。
第三章為研究中實驗設計、製程設備以及量測系統原理的撰寫，其中製程設備主要包含奈米球微影技術(nano-sphere lithography)、電感耦合式乾蝕刻系統(ICP-RIE)、原子層沉積系統(ALD)以及脈衝噴塗技術(Nano- and Micro- particle pulsed-spray coating)等。量測系統將介紹光致激發系統(PL)以及光致激發時間解析系統(TRPL)的架設與原理。
第四章內容主要分成三部分介紹，包括混合型量子點奈米環微型發光二極體製程介紹、原子層沉積鈍化層修復實驗以及利用非輻射能量轉移達到色彩轉換研究之量測結果的分析與討論。第一部份，混合型量子點奈米環微型發光二極體製程內容主要是利用奈米球微影技術，通過電子鎗真空蒸鍍系統(E-Gun System)與電感耦合式乾蝕刻系統步驟，在發光二極體上製造出奈米環結構，並將發光層(multiple quantum wells)蝕刻露出。在奈米結構製程完成後，以原子層沉積方式分別沉積上不同厚度(0、1、3、5與7奈米)的氧化鋁鈍化層以修復經蝕刻後所產生的表面損傷。隨後再藉由脈衝噴塗技術將量子點均勻的噴灑在奈米環發光二極體上。第二部分，實驗分別以光致激發光譜儀系統與時間解析光致發光光譜儀系統進行樣品量測。在隨著氧化鋁鈍化層厚度的增加，經光致發光量測結果分析發現，鍍上7奈米氧化鋁鈍化層的樣品對比沒有鍍鈍化層的樣品，強度上提升了將近五倍。時間解析光致激發系統中也得到隨著鈍化層厚度的增加，量子井的生命週期隨之變短，表示在量子井中載子間的複合機率提升。第三部分，主要在探討量子井與量子點間非輻射能量轉移的現象，使用時間解析光致發光系統分別對焦在量子井與量子點上，觀察其互相能量轉移效率的機制。
第五章主要敘述本研究的結論以及未來方向。

關鍵字

微型發光二極體 ； 非輻射能量轉移 ； 原子層沉積 ； 奈米結構 ； 微型顯示器

並列摘要

In recent years, the development of micro-LEDs (μ-LEDs) has been mainly applied to displays, and its design is to change the process of light-emitting diodes (LEDs), including miniaturization, arraying and thinning. In the process, the size of a single μ-LED chip is only about 1~30 μm. In the process of the LEDs device, the surface damages caused by the dry etching process will produce defects, which will capture the carrier and reduce the probability of electron-hole recombination, thereby leading to the LEDs have lower luminous efficiency. As the devices are micronized, the effects of defects on the devices will become more apparent. The experimental process mainly uses the nano-sphere lithography technology to fabricate the nano-ring structure on LEDs, and combines with quantum dots (QDs) to produce hybrid quantum dot nano-ring micro-LEDs (QD-NR-μ-LEDs) through the non-radiative energy transfer (NRET). Among them, the experiment of atomic layer deposition for passivation layer deposition and the mechanism of NRET between quantum wells (MQWs) and QDs to achieve color conversion will be discussed, and it is expected to be applied to micro-display in the future.
The Chapter 1 contains the advantages of light-emitting diodes, the application of LEDs and the advantages of III-Nitride materials, and a brief introduction to the motivation of this experiment.
The Chapter 2 mainly introduces the principle of the LEDs and presents QDs materials (CdSe/ZnS) in the research, and discusses the NRET dynamics mechanism.
The Chapter 3 is the study of experimental set-up, process equipment and measurement system principle. The process equipment mainly includes nano-sphere lithography, inductively coupled plasma-reactive ion etching (ICP-RIE), atom layer deposition system (ALD) and pulsed-spray coater. The measurement system will be introduced to the construction and principle of the photoluminescence system (PL) and the time-resolved photoluminescence system (TRPL).
The Chapter 4, the content is mainly divided into three parts, including the introduction of the hybrid QD-NR-μ-LEDs process, the experiment about the passivation layer deposited by ALD repairs surface damages, and the measurement results of the color-conversion research through NRET. In the first part, the hybrid QD-NR-μ-LEDs process mainly uses the nano-sphere lithography technology. Through the processes of electron beam evaporation (E-Gun) and the ICP-RIE system, a nano-ring structure is fabricated on the LEDs, and MQWs are etched out. After the nano-ring structure process is completed, Al2O3 passivation layers of different thicknesses (0, 1, 3, 5, and 7 nm) are deposited by ALD to repair surface damages caused by dry etching. And then the QDs are uniformly sprayed onto the nano-ring LEDs by pulse spraying. In the second part, the samples were measured by PL spectrometer and TRPL spectrometer system. With the increasing of the thickness of the passivation layer of Al2O3, the PL intensity show that the sample with 7 nm passivation layer is nearly five times stronger than the sample without passivation layer. In the TRPL system, as the thickness of the passivation layer increasing, the lifetime of the MQWs becomes shorter, indicating that the recombination probability between the carriers in the MQWs is enhancing. The third part is mainly to investigate the phenomenon of NRET between MQWs and QDs. The TRPL system is used to focus on MQWs and QDs separately, and observe the mechanism of their mutual energy transfer efficiency.
The Chapter 5 mainly describes the conclusions of this study and the future works.

並列關鍵字

Micro-LEDs ； Non-radiative energy transfer ； Atomic layer deposition ； Nano-structure ； Micro-display

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