臺灣博碩士論文加值系統

本論文旨在針對氮化鎵系列之蕭特基二極體(Schottky barrier diodes, SBDs)及發光二極體(light emitting diodes, LEDs)進行垂直結構化，以提昇氮化鎵系列元件之電特性、發光效率、及熱散失效果。對於垂直元件結構之表面更進一步進行適當之蝕刻處理，改變元件表面形狀，及探尋優質導電特性金屬，使元件內部之電流或發光分佈更均勻。並於元件研製完成之後進行其熱特性量測及熱行為分析。
於氮化鎵蕭基二極體方面，我們提出一種利用電鍍鎳(nickel electroplating)及雷射剝離(laser lif-off, LLO)技術完成氮化鎵蕭基二極體垂直結構化。利用電鍍鎳及雷射剝離技術，應用於氮化鎵發光二極體之垂直結構化，同樣可以達到減少元件內部電流擁擠效應及降低串聯電阻的作用，進而提升發光效率。為解決垂直結構化LEDs電流擁擠發光不均勻的問題，我們提出改變垂直結構元件表面形狀結合具有低電阻率、高透光率、匹配折射率之銦鋅氧化物(IZO)透明導電層(TCL)促使電流路徑電阻均勻化，達到電流均勻分佈之目的。首先，提出利用非等向雷射蝕刻（Anisotropic Laser Etching）漸變表面磊晶層厚度結合TCL之方法，達到電流及發光分佈均勻化之目的，實驗完成之元件所量測得到之光輸出功率（Light output power）較一般垂直發光二極體提升了38%~26%。進而提出一製程簡單、成本低廉、及可以批次作業(整批處理)之非等向ICP蝕刻技術，於GaN層製得mesa surface結構結合TCL，再利用IZO與n-GaN接面呈現蕭特基接觸特性用於電流遮蔽，可同樣達成電流及發光分佈均勻化目的。藉由此一結構設計並實驗完成之元件所量測得到之光輸出功率（Light output power）較一般垂直發光二極體提升提升了25%光輸出功率。
本論文也提出一以即時資料擷取(data acquisition, DAQ)系統進行發光二極體之接面溫度及其熱阻量測，以分析該封裝完成元件之熱阻（thermal resistance）、熱電容（thermal capacitance）、及熱等效線路模式（thermal equivalent circuit model），提出一個評估封裝完成LED元件之發熱行為模式、熱散失路徑、及熱流瓶頸之新穎方法。並利用LED接面溫度暫態曲線之響應，藉由PSPICE線路模擬以確立熱散失器之熱阻及熱電容關係。
總而言之，本研究論文除了致力於元件垂直結構化研製，進而提出結合非等向雷射蝕刻、非等向ICP蝕刻與TCL達到電流路徑電阻均勻化之目的，局部性的Ti蒸鍍使透明之IZO兼具電流擴散及電流遮蔽作用，解決了電極下方電流擁擠密集發光卻又被電極所阻擋之缺點，提升光輸出功率與發光效率；並且建構一利用即時資料擷取系統，以量測LED元件之接面溫度、熱阻、及熱行為模式分析。

In this dissertation, vertical structure GaN-based Schottky barrier diodes (SBDs) and light emitting diodes (LEDs) were investigated. Vertical-conducting GaN-based SBDs and LEDs were designed, fabricated and characterized, by means of Ni-electroplating substrate transformation in conjunction with laser lift-off technique. A real-time data acquisition (DAQ) technique was also developed for precisely characterizing the junction temperature, light output power, and thermal resistance of light emitting diodes (LEDs).
To further promote both contact and current spreading properties of GaN-based SBDs and LEDs, properly surface etching treatment to the top n-GaN layer and high quality metallic contact system were both proposed. Finally, thermal behavior and thermal model of the fabricated devices were analyzed and developed for further investigating their efficiency and reliability.
To equalize the resistance of all possible current paths in the fabricated Vertical-conducting Metal-substrate GaN-based Light-Emitting Diodes (VM-LEDs), an anisotropic laser etching to the surface layer (n-GaN) of 40-mil VM-LEDs for improving light emission uniformity and light output power is proposed and demonstrated. Typical improvement in light output power by 38-26% has been obtained. A cost effective ICP mesa etching associated with the IZO TCL was also proposed to serve both as current spreading and current blocking. In experiments, VM-LEDs with the proposed structure have been successfully fabricated and an average improvement in light output power by about 25% has also been obtained. A real-time data acquisition (DAQ) technique was developed for precisely characterizing the junction temperature, light output power, and thermal resistance of light emitting diodes (LEDs). Furthermore, by using the transient state of Tj, thermal resistance and thermal capacitance of LEDs were extracted.

Chinese abstract …… i
English abstract …… iii
Acknowledgements (Chinese) …… v
Contents…… vi
Table captions…… xiii
Figure captions…… ix
Chapter 1 Introduction
1-1Electrical properties and current progress of GaN… 1
1-2Current progress in GaN-based light-emitting diodes…4
1-3Organization of the dissertation…7
Chapter 2 Fabrication of Vertical Structure Schottky Barrier Diodes Using Electroplating Nickel Substrate
2-1substrate engineering for vertical-structured GaN-based SBDs…19
2-2Experiments and results… 24
2-3Summary…30
Chapter 3 Simulations of Current and Light Emission Distribution for VM-LEDs with Various Structure Designs
3-1ISE-TCAD simulation tool and models consideration… 53
3-2Design and simulation of various structures …57
3-3Summary…62
Chapter 4 Use of Device Structure Designs to Improve Light Output Performance of VM-LEDs
4-1Samples preparation…75
4-2Fabrication of VM-LEDs with Graded TCL/n-GaN
surface structure78
4-3Fabrication of VM-LEDs with current blocking and
mesa TCL/n-GaN surface structure…82
Chapter 5 Use of a Real-Time DAQ Technique for the Precise Measurement of Junction Temperature and Thermal Resistance of High-Power LEDs
5-1Introduction…101
5-2Motivation…103
5-3Theory background…103
5-4Experiments…104
5-5Summary…108
Chapter 6 Conclusions and future work
6-1Conclusions…121
6-2Suggestions for future work…122
Publication list…124
Vita…127

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