量子井結構上製作金屬奈米顆粒 並研究所產生之表面電漿子與量子井耦合現象

Abstract

為瞭解表面電漿子與量子井耦合以提升發光二極體效率之物理機制，我們首先在氮化銦鎵/氮化鎵量子井結構上，使用聚苯乙烯奈米球微影技術製作金和銀的金屬奈米顆粒。以此技術，我們可以有效控制金屬顆粒的大小和表面覆蓋率。本研究中我們選擇適當大小的聚苯乙烯奈米球，且適當的調整熱退火條件，可以製作出侷域表面電漿子共振波長與量子井發光波段吻合的銀奈米顆粒。經由銀奈米顆粒所產生的侷域表面電漿子與量子井的耦合，不僅加速了量子井中自由載子的發光結合速率，也增強量子井光致螢光的發光強度。經由此耦合的機制，我們也觀察到光致螢光的發光頻譜紅移與光致螢光的衰減時間縮短的現象。隨溫度變化的光致螢光量測結果也顯示量子井內部量子效率的增強效果。

The fabrications of Au and Ag nanoparticles (NPs) with controlled geometry and surface density on a GaN epitaxial structure containing InGaN/GaN quantum wells (QWs) based on polystyrene nanosphere (NS) lithography and the characterizations of their localized surface plasmon (LSP) coupling behaviors with the QWs are demonstrated. By using an appropriate polystyrene NS size and adjusting the post-fabrication thermal annealing condition, the induced LSP resonance wavelength of the fabricated Ag NPs on GaN can roughly match with the QW emission wavelength for generating coherent coupling between the radiating dipoles in the QWs and the induced LSP. The coupling leads to the enhancement of radiative recombination rate of free carriers in the QWs and results in increased photoluminescence (PL) intensity, PL red shift, and PL decay time reduction. Temperature-dependent PL measurement also shows the increase of QW emission internal quantum efficiency through the coupling mechanism.