单根掺杂GaAs纳米线的拉曼光谱研究

We are going to use optical techniques to investigate single undoped and Si, Be doped GaAs nanowires. By using Raman，Brillouin and Photoluminescence (PL) methods, we are going to observe acoustic and optical phonons including transversal(TO) and longitudinal(LO) optical phonons, to determine elastic properties of nanowires from acoustic phonons, to observe multi order LO phonon modes and obtain the coupling between phonons and electrons under resonant Raman scattering. By Raman local vibrational modes(LVM), the detailed doping element incorporation position into Ga sites or As sites of the host GaAs lattice, and the resulting P type or N type doping can be investigated. Using LVM intensity,the corresponding carrier density can be found. By PL spectrum, we are going to observe different exciton peaks of wurtzite and zinc-blende crystal structure of GaAs nanowires, the broadening PL spectrum and frequency shift of doped GaAs nanowires can be used to understand the effect of doping. This project not only investigates the fundamental optoelectronic and elastic properties of doped GaAs nanowires but also has its practical applications in nano optoelectronic devices by constructing the relation between doping elements and carrier density.

本项目拟使用具有闪锌矿和铅锌矿结构的砷化镓纳米线，以及掺杂了不同浓度的Si和Be的砷化镓纳米线，通过拉曼布里渊散射和光致发光等光学方法，研究砷化镓纳米线中声子及其与载流子的相互作用。在实验上通过观测单根砷化镓纳米线的纵/横声学声子，研究其机械性质；在共振条件下，观测纵光学声子的多级谱，研究声子和电子的耦合强度。通过拉曼局域振动模，探索不同浓度掺杂的Si和Be原子在砷化镓晶格中的具体替位细节，以及所形成P型或N型掺杂。通过光致发光实验，观测闪锌矿和铅锌矿结构砷化镓纳米线不同的激子峰，观测Si, Be掺杂砷化镓纳米线光致发光谱中的谱线变宽，峰值移动的现象，定性了解掺杂所带来的各种缺陷，并进一步定量了解光致发光谱的变化与Si, Be掺杂浓度的关系。本项目不仅从基础物理方面理解砷化镓纳米线的光电机械性质，而且通过确定掺杂浓度与所产生载流子类型和浓度的关系，可以进一步用于研制纳米光电器件。

低维半导体材料的基本性质一直是凝聚态物理中的一个重要方向和研究热点，本项目主要研究砷化镓纳米线的晶体结构和能带结构在各项同性的静水压下的表现。 闪锌矿结构的砷化镓纳米线是一种亚稳相，在高压下，我们使用532纳米和488纳米的激光，通过共振拉曼的方法，可以得到其直接带隙和晶体场劈裂随压强的变化分别为0.087 eV/GPa和0.084 eV/GPa。随着压强的增加，在19.2GPa，拉曼和同步辐射同时可探测到闪锌矿结构开始转变，拟合同步辐射结构可知新相为正交相，在21GPa是相变完成。同时，通过拉曼探测到纵横光学模式随压强的变化，得到闪锌矿砷化镓纳米线的Gruneisen参数。

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