Thin-GaN發光二極體電性改善之研究

The Improvement of Electrical Characteristic in Thin-GaN Light-Emitting Diodes

許建祺(Chien-Chi Hsu)

指導教授 ： 張正陽

國立中央大學/理學院/光電科學研究所/碩士(2008年)

摘要

以氮化鎵為基礎之發光二極體(GaN-based LED)的晶粒製程技術主要分為傳統的打線(Wire-Bonding)封裝製程、覆晶(Flip-Chip)製程以及thin-GaN製程等技術，由於藍寶石(Sapphire)基板之高熱阻使得傳統打線、覆晶製程不適用於高功率操作之LED。本論文主要研究thin-GaN製程，以晶圓鍵合(Wafer Bonding)技術與雷射剝離(Laser Lift-Off)技術，將氮化鎵薄膜封裝於導熱效果較佳之矽(Si)基板上。
在製作thin-GaN LED中，發現鈍化層(Passivation)完整性與緻密性會對LED之逆偏漏電流(Reverse Leakage Current)造成影響，而電漿損害(Plasma Damage)以及高串聯電阻(Series Resistance)也會破壞LED之順向偏壓(Forward Voltage)。針對改善thin-GaN LED之逆偏漏電流，我們利用高緻密性之二氧化矽(SiO2)做為鈍化層，成功將thin-GaN LED在-5V逆向偏壓之漏電流降至-0.15?A；在改善thin-GaN LED之順向偏壓，製作Ni薄膜避免電漿損害，以及移除未摻雜氮化鎵(u-GaN Removal)薄膜降低串聯電阻，有效下降thin-GaN LED之順向偏壓。
在我們製作之thin-GaN LED中，順向偏壓最佳約為3.6V，相較於文獻有改善空間；而本研究使用晶圓鍵合與雷射剝離技術，對thin-GaN LED建立製程平台，並改善thin-GaN LED之電特性表現。

關鍵字

電性改善 ； 雷射剝離 ； thin-GaN發光二極體

並列摘要

Chip process technology of GaN-based light-emitting diodes includes wire-bonding, flip-chip, thin-GaN, and so on. However, wire-bonding and flip-chip are inappropriate for high-power LED chips due to high thermal resistance of sapphire substrates. In this thesis, the GaN thin flim is packaged on a material with higher thermal conductivity, silicon substrates, by wafer bonding technology and laser lift-off.
In the fabrication process of thin-GaN LED, we discover that the coverage and the denseness of passivation effect the reverse leakage current of LED. Further, plasma damage and series resistance also degrade the forward voltage of LED. To improve the leakage current of thin-GaN LED, a highly dense passivation made of SiO2 is utilized; leakage current achieves -0.15uA at reverse voltage of -5V. Also, Ni thin film applied to avoid damage caused by plasma is in order to ameliorate the forward voltage of thin-GaN LED. Moreover, decrease of series resistance is achieved by u-GaN removal, which is to reduce the forward voltage of thin-GaN LED.
The best forward voltage of our fabricated thin-GaN LED is 3.6V approximately; nevertheless, it still need to be improved more compared to the reference. A platform of thin-GaN LED chip process is established for improving the electrical characteristics of thin-GaN LED is utilized by wafer bonding and laser lift-off.

並列關鍵字

thin-GaN LEDs ； improvement of electrical characteristics ； laser lift-off

參考文獻

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