以變溫時域螢光量測探討氮化銦鎵/氮化鎵量子井與表面銀奈米顆粒的表面電漿子耦合行為

Abstract

我們使用三種不同銦濃度(不同發光波長)並具有不同內部量子效率的氮化銦鎵/氮化鎵量子井樣品來探討變溫下其不同的時間解析光激發螢光行為，我們尤其要研究在樣品表面沉積銀奈米顆粒產生表面電漿子耦合下這三個量子井樣品的發光行為。利用兩項一次指數函數模型來擬合時間解析光激發螢光消退曲線以及連續波的光致發光頻譜變溫強度變化，我們可以獲得隨溫度變化的螢光衰減時間。我們可以取得各溫度下整體、輻射和非輻射的光致發光衰減時間。這些隨溫度變化的衰減時間，都與富銦團聚的氮化銦鎵量子井結構有關，其中，主要是光子在侷域態和自由載子態之間的轉移乃為重要因素。載子可以透過表面電漿子耦合的效應將能量轉移至表面電漿子共振中以增強其發光，由此，相關載子密度能量分布重整，因而改變了時間解析光激發螢光行為。

Three InGaN/GaN quantum well (QW) samples of different indium contents or emission wavelengths and different internal quantum efficiencies (IQEs) are used for demonstrating different temperature-dependent time-resolved photoluminescence (TRPL) behaviors. In particular, surface Ag nanoparticles (NPs) are deposited onto the sample surfaces for inducing surface plasmon (SP) coupling to compare different effects in those three QW samples. By fitting the photoluminescence (PL) decay profiles with a two single-exponential model and calibrating temperature-dependent decay times based on time-resolved and continuous PL intensity variations, we obtain the overall, radiative, and non-radiative PL decay times as functions of temperature. The temperature-dependent behaviors of those decay times are related to the carrier transport process between localized and free-carrier states, which are formed in an InGaN QW with an indium-rich clustering structure. The SP coupling transfers carrier energy into SP resonance for radiation and hence redistributes energy-dependent carrier density that changes the time-resolved PL behavior.