不同電流阻障層對氮化鎵發光二極體之光電特性研究

Study of Optoelectronic Characteristics of GaN-based LEDs Using Various Current Blocking Layer

莊基陽(Chi-Yang Chuang)

指導教授 ： 郭政煌

國立中央大學/理學院/光電科學研究所碩士在職專班/碩士(2007年)

摘要

改善電流分佈一直是獲取高效率氮化鎵發光二極體(GaN-based LED)的重要議題之一[1]；此外，由於一般結構的發光二極體其p型電極下方所發出的光源，長久以來被本身不透光的材質所遮蔽或反射後被材料所吸收，因此造成光輸出效率的損失。
本篇論文的主要研究目的即為研究數種不同的電流阻障層(current blocking layer, CBL)結構包括二氧化矽(SiO2)、感應耦合電漿蝕刻(Inductively Coupled Plasma etcher)以及離子佈植(Ion implantation)來改善上述LED元件的問題。
首先，為了量化這三種表面處理後的變化，我們製作傳輸線模式(Transmission-line model, TLM)的試片進行量測以換算成串聯電阻，依據SiO2、ICP以及離子佈植等不同製程所獲得的最高串聯電阻分別為3.83×106Ω、6.62×105Ω以及8.36×107Ω。經由製作完成的LED元件量測結果顯示，在光輸出功率方面，利用SiO2、ICP以及離子佈植等三種不同製程的CBL分別提升3.7~9.1%、3.2~7.1%以及5.9~7.2%；然而在電性方面，由於p-GaN有效接觸面積減少，此三種製程依序分別使順向偏壓些微升高0.03~0.09V、0.03~0.07V以及0.03~0.09V。
最後，本論文進一步討論這三種製程所量化的串聯電阻值與CBL結構使用於元件上光輸出功率提升的關係，並探討造成此結果的可能機制。

關鍵字

發光二極體 ； 氮化鎵 ； 電流阻障層

並列摘要

Improving non-uniform current spreading to obtain high light-output efficiency is one of most important topics of GaN-based light emitting diodes (LEDs). Moreover, in conventional design of LEDs, light generated under the opaque p-pad metal contact is absorbed or reflected back by the contact and re-absorbed by material. It will reduce the efficiency of light-output.
The main purpose of this thesis is to investigate three different current blocking layer (CBL) fabrication processes, including deposition of SiO2, Inductively Coupled Plasma (ICP) etching and ion implant to increase the brightness of LEDs.
For qualification the change of these three surface treatments, tested samples with transmission-line model pattern have been applied to acquire the readings of series resistance. The highest resistance readings are 3.83×106Ω, 6.62×105Ω and 8.36×107Ω for SiO2, ICP and ion implant, respectively. Achievements of LED component using CBL structure, we observe the light output power of three kinds of methods are enhanced by 3.7~9.1%, 3.2~7.1% and 5.9~7.2%, respectively. But in electricity property, each process will make forward voltage a slightly higher 0.03~0.09V, 0.03~0.07V and 0.03~0.09V due to decrease of contact surface of p-GaN.
Finally, relation between readings of series resistance and improved light output LEDs with CBL structure has been discussed by these evidences and possible mechanism has been induced in the thesis.

並列關鍵字

LED ； GaN ； current blocking layer

參考文獻

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