高铟组分铟镓氮材料的超快载流子动力学研究

发布时间：2018-10-13 14:54

【摘要】：铟镓氮(InGaN)材料因其带隙随In组分的变化,可在InN的0.7ev和GaN的3.4ev之间任意调节,基本可覆盖整个可见光波段,被认为是新一代制作光电子器件的极好材料。但由于InN和GaN晶格失配导致InGaN材料中存在较严重的相分离,难以制备出高质量的高In组分InGaN材料。这种相分离引起的量子限制效应、能态局域化、态填充等诸多因素使得InGaN的光学性质和载流子动力学过程非常复杂,人们对其物理机制还缺乏深入全面的了解。因此,研究InGaN材料的光学性质不仅有重要的理论意义而且对改善现有发光器件和研制新的器件有非常重要的指导价值。本论文利用稳态荧光光谱、时间分辨荧光和泵浦-探测技术对不同结构的高In组分的InGaN材料的载流子动力学过程进行了细致的研究。本论文的主要内容如下：1.研究了InGaN外延层薄膜在室温下的受激发射及其载流子动力学。在高激发功率下观察到了受激发射现象。并进一步用时间分辨荧光光谱和泵浦-探测技术研究其载流子动力学,获得其荧光寿命衰减曲线和瞬态微分反射率变化曲线,实验结果清晰地展示了光生热载流子较慢的多步弛豫过程物理图像；经过对比发现薄膜样品在受激发射条件下仍具有较慢的载流子热化过程。分析认为这种较慢的载流子热化过程来源于相分离和In凝聚引起的声子瓶颈效应。2.研究了具有不同周期的InGaN多量子阱样品的光致发光性质及其载流子动力学。发现在量子阱样品中也存在着和薄膜材料类似的慢载流子热化过程,认为其来源也是相分离引起的声子瓶颈效应。3.研究了p-i-n结构InGaN多量子阱样品中p-i-n结电场下的荧光复合和载流子动力学过程。我们测量了不同激发功率下p-i-n结构量子阱样品的荧光寿命衰减曲线。发现其荧光衰减过程明显慢于多量子阱和薄膜样品,并且激发功率的变化对辐射复合过程影响明显,分析认为这一现象来源于光生载流子对p-i-n结电场的屏蔽效应和动态去屏蔽效应。
[Abstract]:Indium gallium nitrogen (InGaN) materials can be adjusted arbitrarily between 0.7ev of InN and 3.4ev of GaN because their band gap varies with the composition of In. It can basically cover the whole visible light band and is considered to be an excellent material for making optoelectronic devices in the new generation. However, due to the lattice mismatch between InN and GaN, there is a serious phase separation in InGaN materials, so it is difficult to prepare high quality InGaN materials with high In composition. The quantum confinement effect caused by phase separation, localization of energy states, and state filling make the optical properties and carrier dynamics of InGaN very complicated, and the physical mechanism of InGaN is not fully understood. Therefore, the study of optical properties of InGaN not only has important theoretical significance, but also has a very important guiding value for improving the existing luminescent devices and developing new devices. In this paper, the carrier dynamics of InGaN materials with different structures with high In components were investigated by steady-state fluorescence spectroscopy, time-resolved fluorescence and pump-detection techniques. The main contents of this thesis are as follows: 1. The excited emission and carrier dynamics of InGaN epitaxial films at room temperature have been studied. The phenomenon of stimulated emission was observed at high excitation power. Furthermore, time-resolved fluorescence spectra and pump-detection techniques were used to study the carrier dynamics, and the fluorescence lifetime attenuation curves and transient differential reflectance curves were obtained. The experimental results clearly show the physical images of the multistep relaxation process of photogenerated hot carriers, and it is found that the film samples still have slower carrier heating process under the excited emission condition. It is concluded that this slow carrier heating process originates from the phonon bottleneck effect caused by phase separation and In condensation. 2. The photoluminescence properties and carrier dynamics of InGaN multiple quantum well samples with different periods have been studied. It is found that there is a slow carrier heating process similar to the thin film material in the quantum well samples, and it is considered that the source is also the phonon bottleneck effect caused by phase separation. 3. The fluorescence recombination and carrier dynamics of p-i-n junction in InGaN multiple quantum well samples with p-i-n structure were studied. The fluorescence lifetime decay curves of p-i-n quantum well samples with different excitation power have been measured. It is found that the fluorescence decay process is much slower than that of multiple quantum wells and thin films, and the change of excitation power has an obvious effect on the radiation recombination process. It is considered that this phenomenon originates from the shielding effect of photovoltaic carriers on the p-i-n junction electric field and the dynamic de-shielding effect.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.2

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