Study of injection of spin - polarized electrons into semiconductors through ferromagnetic metal

基于垂直腔面发射激光器(VCSEL)的干叉分叉双稳工作和自旋极化电子的注入，我们主要研究了以下四个方面的内容，以创造新的非线性光学功能器件。(1)研究了正方形波导垂直腔面发射激光器中存在的两个垂直偏振模之间的双稳开关。自饱和系数和交叉饱和系数的相对大小是决定半导体激光器偏振开关特性的关键。数值计算证实，自饱和系数和交叉饱和系数之间的关系满足BALK层和量子阱有源层的偏振双稳条件。利用偏振双稳VCSEL实现了信号的解复用、RZ和NRZ格式的转换等全光信号处理。我们的模拟表明，使用这样的VCSEL可以获得3R功能(重定时、整形和再生)。(3)我们从时间分辨和偏振分辨光致发光估计了漂移通过p-n结的电子的自旋弛豫时间。结果表明，漂移过程中偏振态基本保持不变。(4)用铁磁性金属CoCrN侧电极制作了发光二极管(LED)。然而，LED的光输出是非偏振的。这一结果表明，在GaAs和CoCr界面处极化的电子可能被退极化。

We investigated mainly the following four topics to create new nonlinear optical functional devices based on the pitchfork bifurcation bistable operation of vertical-cavity surface-emitting lasers (VCSELs) and injection of spin-polarized electrons.(1) We studied the bistable switching between the two orthogonal polarization mode existing in the VCSEL with a squared shape waveguide. The relative magnitude of self- and cross-saturation coefficients are crucial to determine the characteristics of polarization switching of laser diodes. The numerical calculation confirmed that the relation between self- and cross saturation coefficients satisfies the condition for polarization bistability in both balk and quantum well active layers. The bistable conduction is satisfied in the wider region for a compressively strained quantum well, especially in the region with large linear gains.(2) All-optical signal processing, such as demultiplexing with a signal bit width conversion function and the conversion between RZ and NRZ formats, were experimentally demonstrated using a polarization bistable VCSEL. We have shown by our simulations that the 3R function (Retiming, Reshaping, and Regenerating) can be obtained using a such VCSEL.(3) We estimated the spin relaxation time of the electrons drifting through the p-n junction from the time- and polarization- resolved photoluminescence. The result showed that the polarization fairly maintained during the drift.(4) We fabricated the light emitting diode (LED) with an n-side electrode made of ferromagnetic metal, CoCr. However, the light output from LED was unpolarized. This result points out that the polarized electrons may be de-polarized at the interface between GaAs and CoCr.