Direct high-speed modulation of circular polarization (Pc) of coherent light will open the way for new communication technology and offers the possibility to overcome the main bottleneck of the optical telecommunications. Here, by using spin-orbit torque (SOT) with spin Hall effect to control the spin injector magnetization, we report for the first time to achieve electrical control of the circular polarization of light emitted from a quantum dot based light emitting diode (LED) at room temperature [1]. The circular polarization can be modulated between ±25% at 250K and ±16% at 290K after pulsed current switching injector magnetization. A repetition of more than 60 times do not reveal any degradation at the injector/semiconductor interface. Our achievement will directly contribute the implementation of the new optical telecommunication technology with Pc modulation.
[1] P. A. Dainone, et al. “Controlling the helicity of light by electrical magnetization switching”, Nature, to be published.
Detection of spin diffusion length in different materials has been launched tremendously so far. But due to the difficulty of obtaining a high-quality semiconductor (SC) layer on ferromagnetic metals, until now most of the studies of spin diffusion transport in SC were only limited on lateral structure devices. Here, by using ultra-high vacuum wafer-bonding technique, a vertical structure of CoFeB/MgO/Si/Pt is fabricated successfully and based on which, the spin diffusion transport is demonstrated at room temperature by spin pumping. With the Pt layer on top to detect the inverse spin hall voltage for different thickness of n-Si layer, the spin diffusion length is determined to be 3.8 μm, which is comparable with the value reported in lateral devices. Furthermore, our experiments reveal the existence of interface state at MgO/Si interface, which is essentially important to build the model of spin-mixing conductance for spin-pumping into Si.
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