表面電極設計對發光二極體光電特性之研究

The Influence of Electrode Pattern on the Optical and Electrical Characteristics of Light-Emitting Diode

楊明傑(Ming-Jie Yang)

指導教授 ： 李有璋

中原大學/工學院/機械工程研究所/碩士(2013年)

https://doi.org/10.6840/CYCU.2013.00365

摘要

由許多文獻指出電極圖形經過設計，可更有效利用多重量子井，提供LED多重量子井較均勻的電流分佈，改善電流壅塞現象與電流壅塞引起之熱影響，進而提升LED的光輸出功率。
本論文透過實驗與數值模擬，探討電極設計對LED發光效率的影響。實驗部分是設計製作延伸p電極，舒解電流擁塞於傳統電極邊緣的現象，然而延伸p電極會遮蔽從主動層所發出的光，故在延伸電極製作洞狀出光結構。從光學量測結果顯示開洞面積越大，光輸出功率越高。本研究設計延伸電極開洞5 μm之LED，最強的光輸出功率為48.1mW，明顯高於傳統LED的43.8 mW，而且在輸入電流500 mA下，傳統與延伸電極開洞5 μm LED的光輸出功率分別為23.7 mW與47.7 mW相較於傳統提升一倍之多，電光轉換效率高於傳統LED約1 %。
模擬部分是使用數值方法模擬LED在主動層的電流密度分佈，並經由電流分佈長度公式修正轉換成光強分佈；最後依此光強分佈以光學軟體進行光線追跡模擬，求解光強度。比對數值模擬結果與實驗結果，顯示模擬與實驗具高度符合。

關鍵字

電極設計 ； 發光二極體

並列摘要

Many studies pointed out that the electrode pattern was designed to use multiple quantum wells more effectively, in which a more uniform current distribution of multiple quantum wells for light emitting diode (LED) is provided to improve the current crowding phenomenon and the thermal influence caused by the current crowding, and thus enhance the light output power of the LED.
In this thesis, experiment and simulation were demonstrated to study the influence of electrode design on the LED luminous efficiency. The extended p-electrode was used to relief the current crowding at the edge of the conventional electrode. However, the extend p-electrode would obscure the light emitted from the active layer, thus hole array with 3 μm and 5 μm diameter were fabricated onto electrodes. The optical measurement showed the larger diameter of hole array has higher light output power. The maximum output power is 48.1 mW for 5 μm hole array LED which is much higher than that of 43.8 mW for the conventional LED. The output power for 5 μm hole array LED (47.7 mW) is almost twice of the conventional LED (23.7 mW) under 500 mA current injection. The electro-optical conversion efficiency is improved nearly 1%.
The numerical analysis was also used to simulate the distribution of current density in the active layer of LEDs. The distribution of current density was transformed to the luminous intensity distribution through the equation of current distribution length. The optical simulation was carried out to solve the light output power through the Monte-Carlo ray tracing. The trend of the numerical simulation demonstrated the consistency with the experimental results.

並列關鍵字

Electrode Pattern ； Light-Emitting Diode

參考文獻

[3] X. Guo and E. F. Schuberta, “Current crowding and optical saturation effects in GaInN/GaN light-emitting diodes grown on insulating substrates”, Applied Physics Letters, Vol. 78, pp. 3337-3340, 2001

[4] J. I. Shim, J. Yun and H. Kim, “Current spreading and its related issues in GaN-based light-emitting diodes”, Proceedings SPIE, Vol. 7216, pp. 72160V-1-72160V-9, 2009.

[5] S. J. Bae, J. Choi, D. H. Kim, I. C. Ju, C. S. Shin, C. G. Ko and J.S. Yu, “Fabrication and theoretical analysis of GaN-based vertical light-emitting diodes”, Semiconductor Science and Technology, Vol. 26, pp. 095008-095014, 2011

[6] C. J. Nuese, J. J. Tietjen, J. J. Gannon and H. F. Gossenberger, “Optimization of electrolumineacent efficiencies for vapor-grow GaAs1-xPx diodes”, Electroluminescent Efficiencies, Vol. 116, pp. 248-253, 1969.

[7] C. Huh, H. S. Kim, S. W. Kim, J. M. Lee, D. J. Kim, I. H. Lee and S. J. Park, “InGaN/GaN multiple quantum well light-emitting diodes with highly transparent Pt thin film contact on p-GaN”, Journal of Applied Physics, Vol. 87, pp. 4464-4466, 2000.