论文摘要
随着全球环保意识的不断增强,含汞的灯具将在2020年左右逐渐退出历史的舞台,最有潜力取而代之的则是AlGaN基深紫外LED。它在照明、杀菌消毒、环境保护、空气水净化以及医疗卫生等领域中有着广泛的应用和重大的市场价值。然而,由于随着A1组分的增大,AlGaN基的深紫外LED将在材料生长和工艺制备上会逐步面临很多挑战。比如外延生长困难,缺陷密度高,p型掺杂与激活困难,光抽取效率低等。在波长短于300 nm的器件中,其外量子效率随着波长的变短迅速降低,无法支持AlGaN深紫外器件市场化。大量研究工作表明,应力对量子阱的发光性质、晶体质量有着深远的影响。本论文围绕AlGaN量子结构材料的发光特性开展了理论和实验研究。从探明AlGaN多量子阱发光不均匀现象的起因出发,开展其光学特性及A1组分偏析的研究。在此基础上,设计并制备量子阱结构以实现量子阱区的应力调控,从而提高量子阱TE偏振光比例,并提高其发光效率。此外,初步开展了 AlGaN微米结构外延生长研究。取得的主要研究成果如下:（1）通过对传统AlG.4Ga0.6N/Al0.5Ga0.5N量子阱结构进行阴极荧光测试发现,量子阱表面发光波长呈现不均匀现象,即在“六角形”结构边缘区域的发光谱峰波长较长,而远离该区域的位置发光波长较短。进而结合拉曼光谱与第一性原理模拟分析,我们推测量子阱表面发光波长呈现不均匀现象主要由以下原因造成:在AlGaN异质外延过程中晶柱的倾斜或者扭转使得晶界处的形成较大的张应力,导致后续的AlGaN量子阱生长过程中,在晶界处由于Ga原子形成能低于A1原子发生了组分偏析现象,即晶界处的Ga组分含量比其它位置来得高,从而使其发光峰位发生了红移。（2）提出在AlGaN多量子阱界面处插入超薄AIN层,以调节量子阱应变状态,从而提高量子阱发光的TE偏振态比例。拉曼光谱测试分析表明,在MQWs界面分别引入一层超薄层和两层超薄层,量子阱的张应变减小了或压应变增加了-1.24 GPa和-1.46 GPa。而发光偏振态测试发现,其发光偏振度从传统量子阱的17.8%分别提高到了 18.5%和22.3%。此外,变温的阴极荧光测试表明,其室温/低温（90K）比值由4.56%分别提高至5.23%和10.66%。由此说明,通过在量子阱界面处引入超薄AIN层可以有效地实现应力场的调节,从而显著提高TE偏振光比例,提高量子阱自发辐射率,为实现高发光效率的深紫外发光器件奠定基础。（3）初步探索了 AlGaN微米柱结构的外延生长。首先采用课题组前期摸索的脉冲生长模式下的自金属催化合成方法外延生长了均匀六方形态GaN微米柱阵列,在此基础上,采用脉冲生长模式生长AlGaN数字混晶微米柱阵列结构。表面形貌测试结果显示,我们以GaN微米柱阵列为模板成功地制备出AlGaN微米柱阵列,其直径在1.5～3μm范围内,密度大约为3.9×l06/cm2。同时,部分微米柱呈现六棱台结构。光学特性分析表明,所生长的六棱台结构AIGaN微米柱上的半极性面发光波长约为260nm,相对于（0001）极性面的发光蓝移了约30 nm。该现象可能是由不同极性面上的AIN、GaN生长速率差异引起的。
论文目录
文章来源
类型: 硕士论文
作者: 路宗艳
导师: 李金钗
关键词: 量子阱,组分偏析,发光偏振特性,微米柱结构
来源: 厦门大学
年度: 2019
分类: 基础科学,信息科技
专业: 物理学,无线电电子学,无线电电子学
单位: 厦门大学
分类号: TN304;O471.1
总页数: 76
文件大小: 6401K
下载量: 36
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