混合型氮化銦鎵/氮化鎵多重量子井之光學特性研究

Optical Studies on Mixed InGaN/GaN Multiple Quantum-well Structures Grown by Metalorganic Chemical Vapor Deposition

洪甯(Ling Hung)

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(2006年)

https://doi.org/10.6342/NTU.2006.01082

摘要

本研究中，我們生長了一系列混合不同層數及不同銦濃度的氮化銦鎵/氮化鎵多重量子井的樣品並量測其光學及結構的特性。首先，在材料結構的分析上包含了電激發螢光光譜、陰極激發螢光光譜、X射線衍射以及高分辨穿透式電子顯像術。其結果分別顯示電洞在這一系列的遷移情況、樣品的品質好壞、不同週期量子井結構之間的差異以及高銦濃度和低銦濃度量子井的銦分佈結果。接著，光學特性量測主要包括光激發螢光光譜以及時間解析之光激發螢光光譜。由光激發螢光光譜的結果顯示，銦濃度較高的氮化銦鎵/氮化鎵量子井樣品內有較多的缺陷以及較強的位能變化與載子侷限效果。而隨著高銦濃度者層數的增加，缺陷密度及載子侷限效果也會跟著增加。然而，由於受到不同濃度以及品質的高銦量子井影響，造成儘管高銦濃度量子井的層數少，但其樣品仍有大量的缺陷及活化能。另外，我們也可以觀察到隨著載子侷限的效果上升，其發光強度與內部量子效應也會跟著提升。由時間解析之光激發螢光光譜的結果顯示，高銦濃度的光激發螢光的衰減時間比低銦濃度要長。主要是因為在高銦濃度的量子井中有較強的壓電場，使得量子侷限史塔克效應較大。而隨著溫度的上昇，載子得到能量跳出區域侷限能階，於是出現兩段不同程度的衰減情形。而衰減時間隨溫度變化的結果顯示，壓電場的強弱以及載子侷限的效應機制之間的競爭會影響載子復合的情形。

關鍵字

混合型氮化銦鎵/氮化鎵 ； 多重量子井 ； 光學特性

並列摘要

In this research, we grow a series of samples by stacking InGaN/GaN quantum wells (QWs) of different compositions in different quantum wells with different indium composition. A series of optical characterization results of the five mixed InGaN/GaN multiple quantum well structures are reported. First, we present systematical material analyses, including electroluminescence, cathodoluminescence, X-ray diffraction, and high-resolution transmission electron microscopy, of the five samples. Then, the PL peak positions and PL integrated intensities show different behaviors of the blue and green emissions in these samples. Furthermore, the Arrhenius plots are fitted to calibrate the activation energy and defect density of these samples. We can generally see that by increasing the number of green-emitting QWs, the defect density and activation energy become higher.
From time-resolved PL (TRPL) measurements, we can generally find that the PL decay time of the green light is longer than that of the blue one. From the results of photon-energy-dependent PL decay time, the longer PL decay times on the low-energy side are partially attributed to the carrier capture from the high-energy localized states. By increasing the temperature, two-component decays, the early-stage decay (faster) time, related to carrier relaxation after they are excited, and the extended decay (slower) decay time, describing the rate of recombination, can be observed. The PL decay times of the green emission as functions of temperature of the five samples show that the decay times generally decrease with temperature. However, some of the decay times increase with increasing temperature. This trend may be attributed to the destruction of excitons and the strong piezoelectric field.

並列關鍵字

mixed InGaN/GaN Multiple Quantum-well Structures

參考文獻

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