氮化銦鎵奈米結構之時間解析螢光光譜研究

Time-Resolved Photoluminescence Study of InGaN Nanostructures

洪誌彰(Chi-Chang Hong)

指導教授 ： 果尚志 ； 安惠榮

國立清華大學/理學院/物理學系/碩士(2008年)

https://doi.org/10.6843/NTHU.2008.00518

摘要

本論文是利用時間解析螢光光譜來探討氮化銦鎵奈米結構﹝薄膜、奈米柱、奈米碟﹞的光學特性。實驗結果主要分為兩部分，一是發光波段為綠光的氮化銦鎵薄膜與奈米柱，二是發光波段為紅光的氮化銦鎵奈米碟。
第一部分的研究，我們以低溫(4.2 K)的時間解析螢光光譜分析氮化銦鎵奈米柱與薄膜，由實驗結果發現氮化銦鎵薄膜的載子鬆弛特性與一般常見氮化銦鎵材料系統相同屬於弱侷限的現象，而氮化銦鎵奈米柱的載子則是受到較強的局限效應影響。變溫螢光光譜的研究結果指出，氮化銦鎵奈米柱的螢光鋒質能量會隨著溫度出現先藍移後紅移之S-shift的現象以及載子受溫度擾動出現去侷限(delocalization)的現象，然而在薄膜之中此現象並不明顯。最後，變溫的時間解析螢光光譜的結果指出氮化銦鎵奈米柱的輻射復合時間(radiative recombination lifetime)在溫度高於100 K時與溫度的二分之三次方成正比，此結果指出在溫度高於100 K以後氮化銦鎵奈米柱的發光機制主要來源為自由激子復合(free exciton recombination)，對於薄膜而言，輻射復合時間與溫度並無此正比關係，我們認為薄膜的發光主要是由自由載子復合所產生的。
第二部分的研究，我們利用不同收光方向(0度正向與90度側向)的低溫(4.2 K)與室溫的螢光光譜以及時間解析螢光光譜來分析氮化銦加奈米碟的光學特性，發現90度側向收光的螢光復合時間較正向收光來的長，此結果指出成長於氮化鎵奈米柱之氮化銦鎵奈米碟異質結構所發出的螢光具有共振腔(cavity)效應。

關鍵字

時間解析螢光光譜 ； 氮化銦鎵 ； 奈米結構 ； 載子複合

並列摘要

InGaN nanostructures which included nanorods, epilayer, and nanodisks were studied by time-resolved photoluminescence (TRPL) measurement. This master thesis contains two parts of experimental results. One is the bright green emission from InGaN nanorods compared to InGaN epilayer. The other one is the investigation of optical properties of InGaN disk. In part one, based on the low temperature time-resolved emission spectrum and the temperature dependence of photoluminescence (PL) and TRPL, carriers are found to be strongly confined and free excitonic behaviors at room temperature in InGaN/GaN rods heterostructure, which may causes highly brightness green luminescence emission in InGaN/GaN rods. In the part two, we found an evidence of the cavity effect in InGaN disk measured by TRPL at low temperature. PL and TRPL measured at normal and along the nanorods at room and low-temperature, confirm that cavity effect exists in InGaN disk with GaN nanorods. Currently, we cannot precisely defined Purcell factor in our system yet. This is become of long PL decay time of pure InGaN disk luminescence which exceeds our instrument limitation and two PL decay times in InGaN disk with GaN nanorods at normal detection. Nevertheless, a qualitative description of Purcell effect and confirm cavity effect in InGaN disk/GaN nanorods are given.

並列關鍵字

time-resolved photoluminescence ； InGaN ； nanostructure ； carrier recombination

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