具有銀奈米光柵薄p-型層綠光發光二極體的表面電漿子耦合效應

Abstract

在本研究中，我們於綠光發光二極體之p-型氮化鎵層上製作不同凹槽深度及寬度的銀奈米光柵結構，利用此結構產生的表面電漿子共振和發光二極體之量子井耦合。為了讓金屬光柵在平面波入射時，可以提供表面電漿子動量匹配，以激發表面電漿極化子，我們特別計算所需的金屬光柵週期。實驗中，我們利用電子束微影搭配乾蝕刻技術在發光二極體上製作可變化金屬脊寬度和高度的光柵，當平面波入射時，可同時激發表面電漿極化子和侷域表面電漿子共振，我們藉由反射頻譜量測分析表面電漿子的特徵。當表面的銀光柵結構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，也可以減少載子的生命週期並降低發光效率在元件注入高電流時的滑落效應，同時也可以提高調變頻寬。此外，我們也利用數值模擬結果來辨別金屬光柵結構激發的模態是表面電漿極化子或侷域表面電漿子。一般而言，隨著金屬脊結構高度越小或寬度越大，表面電漿極化子模態較容易激發。

The surface plasmon (SP) coupling effects of an Ag grating structure on the top of a green-emitting single-quantum-well (QW) light-emitting diode (LED) are demonstrated. The grating period is designed for momentum-matching the surface plasmon polariton (SPP) with an incident plane wave. Ag gratings of different ridge depths and widths are fabricated for exciting both SPP and localized surface plasmon (LSP) resonances and comparing their different SP coupling behaviors. It is found that when an SP resonance mode, either SPP or LSP, coincides with the QW emission wavelength, the internal quantum efficiency is enhanced, electroluminescence intensity is increased, and the efficiency droop effect is reduced. Numerical simulations are performed for identifying either SPP or LSP mode excited in such an Ag grating structure. Generally speaking, an SPP mode can be more easily excited when the grating ridge depth is small and ridge width is large.