Bi诱导GaAs纳米线形成的缺陷及其调控的光学极化特性的研究

Due to their unusual optical and electronic properties, semiconductor nanowire (NW) from III-V semiconductors structures， for example，GaAs NWs have attracted much attention as a building block for a new generation of electronic and optoelectronic devices such as nano-lasers, solar-cell and photodetectors for several decades. By incorporation Bi into GaAs NWs, the band gap can not only be tuned to the attractive optical fiber communication wavelength 1.3 μm (0.95 eV) and 1.55μm (0.80 eV), but also create new defect structure, which can be employed to control the degree of linear optical polarization. Meantime, chemical identification of the defect in Bi induced GaAs NWs would help optimize the growth of GaAsBI NWs. The objectives of this research program are the following: 1) How to probe the effect of Bi content and the formation of defect on the band structure and carrier relaxation of the single GaAsBi nanowire grown by Au-assisted MBE; 2)How to use optical detected magnetic resonance (ODMR) technique to identify of the involved point defects and surface defects which act as a dominant role in the non-radiative recombination process in GaAsBi NWs; 3)How to control optical polarization direction by use of the new crystal defect phase in GaAsBi NWs. This may prove useful in, for example, infrared NW laser, optically gated switches and highly dense optical interconnects in photonic-based circuits, where polarization of emission and detection could increase the information bandwidth.

Bi进入GaAs纳米线不仅能有效的调控其能带带隙向红外波段移动，并且会诱导形成新的晶体缺陷结构，可以用来调控其光学极化偏振方向。同时对Bi进入GaAs纳米线后形成的缺陷进行化学表征，可以为GaAsBi纳米线的优化生长提供理论依据。本项目主要解决以下问题：1）Bi掺入GaAs纳米线后其Bi组分和形成的缺陷结构对其能带结构和载流子复合效率的影响；2）Bi进入GaAs纳米线后形成的缺陷态和表面的缺陷态在载流子复合过程中将作为非辐射复合中心，如何对这些缺陷利用光探测磁共振技术进行化学表征；3）如何利用Bi进入GaAs纳米线后形成的晶体缺陷结构调控其发光偏振极化方向。这些问题的解决为未来在可能的红外纳米偏振光探测和光发射器件方面奠定研究基础。

纳米线可以作为偏振灵敏的光探测器或者纳米尺度的线偏振光源。这种偏振探测灵敏的纳米光探测器和光源其将有可能在纳米光开关，高密集光学互连等应用方面有潜在应用价值。本项目主要利用变温发光激发谱，共振拉曼实验并结合高分辨透射电镜研究金催化分子束外延技术生长的 GaAsBi 纳米线的晶格和能带结构，研究Bi进入GaAs线对其晶体结构，光学偏振特性，能带结构和载流子浓度的影响。通过本项目的工作，对 Bi 进入 GaAs 纳米线形成的缺陷特性及其调控的发光极化特性以及对纳米线的能带结构的影响有更深入的理解。本项目重要结果包括：1）利用分子束外延技术（MBE）成功生长了硅基纳米线阵列衬底以及GaAs和GaAsBi纳米线；2）首先利用偏振依赖的发光谱，发光激发谱，共振拉曼实验并结合高分辨透射电镜研究了纤锌矿（WZ）结构的GaAsBi纳米线能带结构，定量获得了铅锌矿结构的GaAsBi纳米线A，B和C价带的精确位置，同时发现其能带结构对温度不敏感，这对基于GaAsBi纳米线的激光器件的制备非常重要。3）实现了低温下Bi诱导的GaAs纳米线~97%的线偏振极化率，为未来纳米线红外偏振探测和发射提供了可能性。4）发展了一种利用显微拉曼光谱进行无损并可同时进行小尺寸样品的探测载流子浓度的方法，利用这种方法定量确定了Bi进入GaAs后诱导的缺陷引起的空穴载流子浓度。上述结果为未来实现偏振敏感的纳米红外光电探测和光发射器件提供了可能性。发表了受本项目资助的SCI期刊文章16篇。培养了1名博士和4名硕士。