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Design and Characterisation of III-V Semiconductor Nanowire Lasers

机译：III-V半导体纳米线激光器的设计与表征

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摘要

The development of small, power-efficient lasers underpins many of the technologies that we utilise today. Semiconductor nanowires are promising for miniaturising lasers to even smaller dimensions. III-V semiconductors, such as Gallium Arsenide (GaAs) and Indium Phosphide (InP), are the most widely used materials for optoelectronic devices and so the development of nanowire lasers based on these materials is expected to have technologically significant outcomes.;This PhD dissertation presents a comprehensive study of the design of III-V semiconductor nanowire lasers, with bulk and quantum confined active regions. Based on the design, various III-V semiconductor nanowire lasers are demonstrated, namely, GaAs nanowire lasers, GaAs/AlGaAs multi-quantum well (MQW) nanowire lasers and InP nanowire lasers. These nanowire lasers are shown to operate at room temperature, have low thresholds, and lase from different transverse modes. The structural and optoelectronic quality of nanowire lasers are characterised via electron microscopy and photoluminescence spectroscopic techniques. Lasing is characterised in all these devices by optical pumping. The lasing characteristics are analysed by rate equation modelling and the lasing mode(s) in these devices is characterised by threshold gain modelling, polarisation measurements and Fourier plane imaging.;Firstly, GaAs nanowire lasers that operate at room temperature are demonstrated. This is achieved by determining the optimal nanowire diameter to reduce threshold gain and by passivating nanowires to improve their quantum efficiency (QE). High-quality surface passivated GaAs nanowires of suitable diameters are grown. The growth procedure is tailored to improve both QE and structural uniformity of nanowires. Room-temperature lasing is demonstrated from individual nanowires and lasing is characterised to be from TM01 mode by threshold gain modelling.;To lower threshold even further, nanowire lasers with GaAs/AlGaAs coaxial multi-quantum well (MQW) gain regions are investigated. The TE01 mode, due to its polarisation and excellent overlap with the gain region, is predicted to lase in these nanowire heterostructures. Through gain/loss calculations, important design criteria, such as the optimal well thickness to minimise the threshold carrier density and the optimal number of QWs to minimise the threshold fluence are determined. Based on the design, MQW nanowire heterostructures containing eight uniform coaxial GaAs/AlGaAs MQWs are grown. Room-temperature lasing is demonstrated from individual nanowires at a threshold fluence that is two times lower compared to the bulk GaAs nanowire lasers. Lasing is also verified to be from TE01 mode by polarisation measurements.;Lastly, a mode characterisation technique based on imaging the polarisation dependent far-field emission pattern of nanowire lasers is presented. To demonstrate this technique, InP nanowire lasers are used, because of their excellent structural characteristics. The InP nanowire lasers are designed to lase from different guided modes by varying the nanowire diameter. The experimentally obtained polarisation dependent far-field profiles match very well with numerical simulations and enable unambiguous identification of the lasing mode(s) in nanowire lasers.;Overall, this thesis presents extensive modelling of nanowire lasers, which is supported by experimental results. The modelling will provide a useful reference for developing novel nanoscale lasers and improving the performance of current nanowire lasers.
机译：小型，高能效激光器的发展巩固了我们今天使用的许多技术。半导体纳米线有望将激光小型化至更小的尺寸。 III-V半导体，例如砷化镓（GaAs）和磷化铟（InP），是光电设备中使用最广泛的材料，因此，基于这些材料的纳米线激光器的开发有望在技术上取得重大成果。论文对III-V族半导体纳米线激光器的设计进行了全面的研究，该激光器具有块状和量子限制的有源区。基于该设计，展示了各种III-V半导体纳米线激光器，即GaAs纳米线激光器，GaAs / AlGaAs多量子阱（MQW）纳米线激光器和InP纳米线激光器。这些纳米线激光器显示在室温下运行，具有较低的阈值，并且具有来自不同横向模式的激光。纳米线激光器的结构和光电质量通过电子显微镜和光致发光光谱技术表征。在所有这些设备中，激光的特征都是光泵浦。通过速率方程模型分析激光特性，并通过阈值增益建模，偏振测量和傅立叶平面成像来表征这些器件的激光模式。首先，证明了在室温下工作的GaAs纳米线激光器。这是通过确定最佳纳米线直径以减少阈值增益并钝化纳米线以提高其量子效率（QE）来实现的。生长具有合适直径的高质量表面钝化GaAs纳米线。量身定制生长程序以提高纳米线的QE和结构均匀性。通过阈值增益建模从单个纳米线演示了室温激光，并且通过阈值增益建模将激光表征为TM01模式。为了进一步降低阈值，研究了具有GaAs / AlGaAs同轴多量子阱（MQW）增益区域的纳米线激光器。由于其极化和与增益区的极佳重叠，TE01模式预计会在这些纳米线异质结构中产生激光。通过增益/损耗计算，确定了重要的设计标准，例如，最佳的阱厚度以最小化阈值载流子密度，以及最佳的QW数量以最小化阈值通量。基于该设计，生长了包含八个均匀的同轴GaAs / AlGaAs MQW的MQW纳米线异质结构。从单个纳米线以阈值通量证明了室温激射，该阈值通量比块状GaAs纳米线激光器低两倍。通过偏振测量还证明了激光发射是来自TE01模式。最后，提出了一种基于成像纳米线激光器的偏振相关远场发射图案的模式表征技术。为了证明该技术，使用了InP纳米线激光器，因为它们具有出色的结构特性。 InP纳米线激光器设计为通过改变纳米线直径从不同的引导模式发射激光。实验获得的偏振相关的远场轮廓与数值模拟非常吻合，并能够明确识别纳米线激光器中的激光模式。总的来说，本文提出了纳米线激光器的广泛建模，并得到了实验结果的支持。该模型将为开发新型纳米级激光器和改善当前纳米线激光器的性能提供有用的参考。

著录项

  • 作者

    Saxena, Dhruv.;

  • 作者单位

    The Australian National University (Australia).;

  • 授予单位 The Australian National University (Australia).;
  • 学科 Materials science.;Electrical engineering.
  • 学位 Ph.D.
  • 年度 2017
  • 页码 201 p.
  • 总页数 201
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 生理学;
  • 关键词

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