超高速(>1Gb/s)可見光發光二極體應用於塑膠光纖通訊及內部載子動力學的研究

Very high speed (>1Gb/s) visible LED applied for Plastic Optical Fiber communication and investigation of the internal carrier dynamic

林哲緯(Che-wei Lin)

指導教授 ： 許晉瑋

國立中央大學/資訊電機學院/電機工程學系/碩士(2012年)

摘要

本篇論文分為兩大主題，主題一是高速發光二極體應用於塑膠光纖通訊；主題二為紅光發光二極體內部載子動力學的研究。我們展示了新的藍綠光發光二極體其中心波長為500nm，使用圖案化藍寶石為基板作為塑膠光纖通訊的光源。為了增加外部量子效率和輸出功率於此極小尺寸的高速發光二極體，我們採用了圖案化藍寶石為基板。此外，藉由減少主動層InxGa1-xN/GaN量子井的數量和縮小元件發光區域，我們可以得到極高速的電光轉換頻寬(可高達400MHz)於所有高速可見光發光二極體中，並只需一個非常小的直流偏壓電流(40mA)。藉由金屬封裝transistor out-line can (TO-can)整合一個直徑500?m透鏡，會有~4dBm功率的提升從晶片到塑膠光纖，量到的功率高達-2.67dBm在40mA偏壓電流下。超高速無誤的資料傳輸速度(1.07Gbps)在50公尺塑膠光纖已成功的被展示。此外，利用向前錯誤更正(FEC)技術後，已經可於低電流40mA下達到。
此外，為了研究紅光發光二極體(AlGaP-based)的內部載子動力學，我們開發了新穎的Electrical-Optical pump-probe方法。透過直接注入短脈衝電信號激發，此方法可以直觀地得到樣本的光響應波形，以分析其原始的載子動力學。以此方法分析我們的新元件，量測結果顯示，光響應的波形在不同的偏壓電流下是不變的，溫度從室溫到100度。此結果與大多數AlGaP-based紅光LED的研究結果是相反的。由此我們確認了所觀測到的高電流下效率衰退（efficiency droop）現象的主要原因並不是由熱效應引發載子溢出，而是在低偏壓電流下歸因於缺陷的再復合；在高偏壓電流下歸因於缺陷的飽和與自發性複合機制。

關鍵字

塑膠光纖通訊 ； 發光二極體 ； 內部載子動力學

並列摘要

We demonstrate the performance of a novel cyan light-emitting diode (LED) on a patterned sapphire (PS) substrate as a light source for plastic optical fiber (POF) communications with the central wavelength at 500 nm. To further enhance the external quantum efficiency (EQE) and output power of this miniaturized high-speed LED, an LED with a PS substrate is adopted. Furthermore, by greatly reducing the number of active InxGa1-xN/GaN multiple quantum wells (MQWs) to three and minimizing the device active area, we can achieve a record high electrical-to-optical (E-O) bandwidth (as high as 400 MHz) among all the reported high-speed visible LEDs under a very-small DC bias current (40 mA). By use of the transistor out-line can (TO-can) package integrated with a lens (500 ?m diameter), a ~4 dB enhancement in coupled optical power from chip to POF and a measured power as high as -2.67 dBm under 40 mA bias current can be achieved.Very-high error-free 1.07 Gbps data transmission over a 50 m POF fiber has been successfully demonstrated using this device under a bias current of 40 mA with forward error correction (FEC) technique
The mechanism responsible for the efficiency droop in AlGaInP-based vertically structured red light-emitting diodes (LEDs) is investigated using dynamic measurement techniques.
Short electrical pulses ( 100 ps) are pumped into this device and the output optical pulses probed using high-speed photoreceiver circuits. From this, the internal carrier dynamic inside the device can be investigated by use of the measured electrical-to-optical (E-O) impulse responses. Results show that the E-O responses measured under different bias currents are all invariant from room temperature to 100 C. This is contrary to most results reported for AlGaInP-based red LEDs, which usually exhibit a shortening in the response time and degradation in output power with the increase of ambient temperature. According to the
extracted fall-time constants of the E-O impulse responses, the origin of the efficiency droop in our vertical LED structure, which has good heat-sinking, is not due to thermally induced carrier leakage, but rather should be attributed to defect recombination and the saturation of defect/spontaneous recombination processes under low and high bias current, respectively.

並列關鍵字

internal carrier dynamic ； plastic optical fiber ； light emitting diode

參考文獻

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