具有表面銀奈米顆粒及插入介電質層的表面電漿子耦合發光二極體

Surface Plasmon Coupled Light-emitting Diodes with Surface Ag Nanoparticles and Dielectric Interlayers

陳忠輝(Chung-Hui Chen)

指導教授 ： 楊志忠

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2014年)

https://doi.org/10.6342/NTU.2014.10010

摘要

我們透過在p型氮化鎵和銀奈米顆粒間插入折射率較氮化鎵低的介電質中間層，將表面電漿子耦合效應應用在藍色發光二極體上。當p型氮化鎵厚度較薄時，表面的銀奈米顆粒所產生之表面電漿子共振和發光二極體中的量子井耦合，可以提高內部量子效率和發光二極體的發光強度，減少載子的生命週期，降低外部量子效率在元件注入高電流時滑弱的效應，同時提高調變頻率。在銀金屬奈米顆粒及p型氮化鎵間插入低折射率的介電質層，可以使表面電漿子共振波長藍移，藉以提升藍光發光二極體之表面電漿子耦合效果，但當p型氮化鎵厚度較厚時，表面的銀奈米顆粒和量子井距離太遠，表面電漿子耦合效果不明顯，但發光二極體的特性仍會因為銀顆粒增加些微的光萃取效率。本論文中，我們比較表面規則排列和隨機分佈銀奈米顆粒的效果，其中規則排列的銀奈米顆粒可以有波長較專一性的的侷域表面電漿子共振，然而表面電漿子耦合效率取決於侷域表面電漿子在量子井發光波段的共振強度，因此，表面規則排列的銀奈米顆粒產生之表面電漿子耦合效果未必比較強。同時我們也比較單層及多層量子井的表面電漿子耦合效應，結果顯示單層量子井的發光二極體之表面電漿子耦合效應較強，我們認為這是因為多層量子井結構和表面電漿子耦合的效應較不均勻，而且多層量子井本質上其內部量子效率較單層高，因此表面電漿子耦合效應在多層量子井的實驗結果上較不明顯。

關鍵字

銀奈米顆粒 ； 介電質層 ； 表面電漿子 ； 發光二極體

並列摘要

The enhanced surface plasmon (SP) coupling effects in a blue light-emitting diode (LED) with surface Ag nanoparticles (NPs) by adding a dielectric interlayer (DI) of a lower refractive index, when compared with that of GaN, between the Ag NPs and p-GaN is demonstrated. When the p-GaN is reasonably thin, the surface Ag NPs induce SP coupling with the quantum wells (QWs) in the LED, leading to the increases of internal quantum efficiency (IQE) and LED output intensity, the decrease of photoluminescence (PL) decay time, the reduction of the external quantum efficiency (EQE) droop effect, and the increase of modulation cutoff frequency. By adding a DI, the SP coupling effect is enhanced, resulting in the further improvements of all the aforementioned factors. When the p-GaN layer is thick, the weak SP-coupling plus light extraction enhancement can also slightly increase the emission efficiency, reduce the droop effect, and increase the modulation cutoff frequency.
In this study, we also compare the SP coupling effects between the LEDs with regularly patterned (REG) and randomly distributed (RAN) Ag NPs. Although the REG Ag NPs can produce stronger localized surface plasmon (LSP) resonances with narrower spectral widths, the SP coupling effect depends only on the LSP resonance strength at the QW emission wavelength. Meanwhile, we compare the SP coupling effects between the LED samples with single- and multiple-QW. In all cases, the LED performance improvements are more significant through SP coupling in the samples with single-QW. This result can be attributed to the non-uniform SP coupling effects among the QWs in a multiple-QW sample. Also, the higher intrinsic IQE in the samples with multiple QWs can result in a less favorable SP coupling effect.

並列關鍵字

Surface Plasmon ； Ag Nano particles ； Dielectric interlayer

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