氧化銦錫奈米柱狀結構應用於提升氮化鎵發光二極體之出光效率

Abstract

在本文中，我們研究氧化銦錫奈米柱狀結構的生長機制和物理特性，進而應用在發光二極體來提升其光萃取效率。奈米柱狀結構是以電子槍蒸鍍搭配斜向入射氮氣或斜向沉積法來製作。我們使用掃描式電子顯微鏡、穿透式電子顯微鏡、能量散射光譜儀、紫外-可見光光譜儀以及四點探針等儀器來對氧化銦錫奈米結構作結構、成分、光性以及電性上之分析。我們亦使用三維有限時域差分法來計算氧化銦錫奈米柱結構對發光二極體光輸出功率提升的程度的影響。 在論文的第三章，我們主要會討論氧化銦錫奈米柱的生長機制及單根奈米柱的內部組成成分。我們也匯整了在不同沉積條件環境下成長對氧化銦錫奈米柱薄膜外部形貌所造成的影響。在光性上，這層氧化銦錫奈米柱結構薄膜在寬頻域對光都具有優越的穿透特性。而在論文的第四章第五章，我們將高密度分佈的氧化銦錫奈米柱薄膜應用在氮化鎵藍寶石基板型發光二極體和垂直注入型發光二極體上。分別對兩種元件做出光特性的量測，結果顯示出光功率都較原本的元件提升了47.4%和19.1%。我們使用三維有限時域差分法來驗證氧化銦錫奈米柱結構對這兩種發光二極體光輸出功率提升程度的影響。

In this thesis, we studied the growth and characteristics of indium tin oxide (ITO) nanorod structures and applied the nanostructures on light emitting diode (LED) to enhance the light extraction efficiency. The characteristic nanorod formation is achieved by electron-beam evaporation with an obliquely incident nitrogen flux, that is, the so-called glancing angle deposition. The structural morphology, material, electrical, and optical properties were analyzed by various characterization techniques, including Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Energy Dispersive Spectroscopy (EDS), ultraviolet-visible spectrophotometer, four-point probe, etc. We also employed a three-dimensional finite difference time domain (3D-FDTD) method to calculate the enhancement factor of the light output power from the LEDs with ITO nanorods of various heights. In chapter 3, the growth mechanism and the material characteristics of a single ITO nanorod are analyzed. The dependence of the nanostructure morphologies on the deposition conditions is also discussed. The nano-column material exhibits broadband high transmittance spectrum. In chapter 4 and 5, we have applied the high density ITO nanorods on GaN/InGaN sapphire-based LEDs and Vertical-Injection LEDs, respectively. The light output powers are enhanced by a factor of 1.47 and 1.91, respectively. The enhancement factor of the light output power from LEDs with ITO nanorods of various heights was verified by 3D-FDTD simulation, and reasonable agreement with the experimental results has been obtained.