自旋发光二极管的圆偏振光电流谱研究

The spin injection at room temperature in the absence of a magnetic field is the core issue of the investigation on semiconductor spintronics , and the efficiency of spin injection is the key of the spin injection characterization. The measurement of the circular polarization of the emitted light from a spin light-emitting diodes(spin LED) is the general way to characterize the efficiency of spin injection from ferromagnetic metal to semiconductor. While, the following questions cannot be solved by this optical method, involving the measurement of the spin injection efficiency at higher temperature, the relationship between the spin polarized direction and the injection efficiency, the changing of the injection efficiency with the injection depth. Compared to the optical method, circular polarized photo current is observable at room temperature and the spin relaxation mechanism affecting it and the process of the spin injection is similar. So the investigation of the circular polarized photo current can make up the inadequate of the optical measurement in the detection of the spin injection efficiency. By the circular polarized photo current spectrum in different wave length, the spin polarization of different region in spin LED and different energy level in the quantum well can be investigated. By changing the incident angle, the injection efficiency of the spin polarization both perpendicular and along the surface can be investigated in the same device. The combination of the two technologies is helpful for us to understand the spin injection process and the physical mechanism.

实现室温、零磁场下的高自旋注入是研制半导体自旋电子器件的核心问题，而自旋注入效率的测量与表征是研究自旋注入的关键。自旋发光二极管发光的圆偏振极化度是目前表征铁磁金属向半导体的自旋注入效率最常用的方法,但却无法研究如下问题：1）较高温度甚至室温下自旋注入效率的测量及其变化规律；2）自旋注入效率与自旋取向的关系；3）自旋注入效率随注入深度的变化过程。与光学方法相比，圆偏光激发的光电流在室温下可观测，而且影响圆偏振光电流与自旋注入过程的自旋驰豫机制有很多共同之处，因此圆振偏光电流有望成为表征自旋注入效率的方法。自旋发光二极管的圆偏振光电流研究可以弥补光学方法在表征自旋注入效率方面的不足：通过不同波段的圆偏振光电流谱可以研究不同区域和不同能级的自旋极化，通过改变光的入射角可以研究不同方向极化的注入效率。二者结合起来有助于我们深入理解自旋注入行为以及相关的物理机制。

实现室温、零磁场下的高自旋注入是研制半导体自旋电子器件的核心问题，而自旋注入效率的测量与表征是研究自旋注入的关键。自旋发光二极管发光的圆偏振极化度是目前表征铁磁金属向半导体的自旋注入效率最常用的方法,但尚有诸多问题有待解决。针对这些问题，我们开展了如下研究工作： 我们首先建立了自旋发光二极管圆偏振光电流的理论模型；然后从比较简单的铁磁/半导体异质结构出发，阐明铁磁/半导体界面对圆偏振极化光电流的影响；同时研究了与自旋发光二极管铁磁部分结构类似的垂直发射激光器结构的圆偏振极化自旋光电流，揭示铁磁层的存在对自旋发光二极管圆偏振极化光电流的影响；在此基础上我们研究了自旋发光二极管结构的圆偏振光电流随偏压、温度的变化，并通过圆偏振光电流谱研究不同量子阱区域圆偏振极化光电流的差异；最后我们研究了铁磁层极化方向垂直和平行于样品表面时圆偏振极化光电流的区别，阐明自旋发光二极管结构对不同自旋取向的过滤作用。与光学方法相比，圆偏光激发的光电流在室温下可观测，而且影响圆偏振光电流与自旋注入过程的自旋驰豫机制有很多共同之处，因此圆振偏光电流有望成为表征自旋注入效率的方法。自旋发光二极管的圆偏振光电流研究可以弥补光学方法在表征自旋注入效率方面的不足。本课题执行近4 年来，共发表标有课题号（或项目号）的SCI 收录论文11篇，其中包括PHYSICAL REVIEW APPLIED 1 篇， PHYSICAL REVIEW B 1 篇，Scientific Reports 1 篇，ACS PHOTONICS 1 篇，OPTICS EXPRESS 1 篇。