Recent Developments in Silicon Spintronics

Synopsis

The use of spin as a state variable in logic devices has been a long-standing goal among the semiconductor spintronics (SC) research community. The spin field-effect transistor, whose source and drain are ferromagnetic, is one of the key devices in SC spintronics. Its operation is based on the transport and manipulation of spin-polarized carriers in a lateral SC channel. Silicon, owing to its compatibility with the existing complementary metal-oxide semiconductor (CMOS) technology and its long spin coherence, is the natural choice for the transport material in SC spintronic devices. For most of the envisaged Si-based spintronic devices, the key requirements are to electrically create, transport and detect spin-polarized current in the Si channel, all in an efficient manner. To date, the most practical method to achieve spin injection in Si-based devices consists of driving a current from a ferromagnetic (FM) tunnel contact into the Si. Using this approach, all-electrical spin injection, transport, and detection have been demonstrated in Si channels using the nonlocal four-terminal geometry [1,2].

Here, I will discuss several important aspects of such Si-based devices. First, I will show how to achieve efficient spin injection, transport, and detection in a Si channel using Fe/MgO magnetic tunnel contacts [1]. I will then discuss how the tunnel spin polarization of the Fe/MgO contact varies as a function of the MgO thickness and what is the role of symmetry-based spin filtering due to coherent tunneling in Fe/MgO tunnel contacts on Si [2]. Next, I will demonstrate how a drift electric field in a heavily doped Si channel changes the spin transport. In particular, I will provide a simple, general and accurate method to quantify spin drift [6] in Si-based spin transport devices [3]. Finally, I will report on spin transport in 2-terminal Fe/MgO/Si-channel/MgO/Fe lateral spin-valve devices [4,5], which are the most relevant devices for practical applications due to their simple and compact design. The achievement of high spin polarization in Si combined with a comprehensive understanding of the spin-transport properties of the silicon channel, as provided here, is essential to successfully implement Si spintronic devices for beyond CMOS era.

References

[1] A. Spiesser et al., Phys. Rev. Appl. 8, 064023 (2017).

[2] A. Spiesser, et al., Phys. Rev. B 99, 224427 (2019).

[3] A. Spiesser et al., Phys. Rev. Appl. 11, 044020 (2019).

[4] A. Spiesser, et al.,  Appl. Phys. Lett. 114, 242401 (2019).

[5] R. Jansen, A. Spiesser, et al., Phys. Rev. B 104, 144419 (2021).

Biography

Dr. Aurelie Spiesser is a Senior Research Scientist in the Research Center for Emerging Computing Technologies at the National Institute of Advanced Industrial Science and Technology (AIST) in Tsukuba, Japan. She received her PhD in Physics and Materials Science from Aix-Marseille University in France in 2011. After that, she was awarded a Postdoctoral Fellowship from the Japanese Society for the Promotion of Science (JSPS) to develop Si-based spintronics devices in the Spintronics Research Center at AIST. In 2014, she was appointed as a tenured Research Scientist at AIST. Her research activities focus on developing approaches to inject, transport and detect spin-polarized carriers in Si-based devices, and exploring new routes to control and manipulate spins in semiconductors. A long-term goal of hers is to develop methods to use spin as an information carrier in Si-based electronics for high-density, ultralow power logic devices. 

Aurelie has expertise in thin film growth, device fabrication, and in structural, electric, and magnetic characterizations of nanostructures based on ferromagnets, oxides and semiconductors. She has published 40+ technical articles in peer-reviewed journals. In 2009, she was honored by the L’Oreal-UNESCO-French Academy of Sciences in the national program “For Women in Science”. She is also a member of the Japanese Society of Applied Physics, the Magnetic Society of Japan and the IEEE Magnetics Society.