Spin injection through energy-band symmetry matching with high spin polarization in atomically controlled ferromagnet/ferromagnet/semiconductor structures

Michihiro Yamada,Makoto Tsukahara,Kohei Hamaya,Fumiaki Kuroda,Tetsuya Fukushima,Shinya Yamada,Tamio Oguchi,Kentarou Sawano

doi:10.1038/s41427-020-0228-5

Abstract

Electrical injection of spin-polarized electrons from ferromagnets into semiconductors has been generally demonstrated through a tunneling process with insulator barrier layers that can dominate the device performance, including the electric power at the electrodes. Here, we show an efficient spin injection technique for a semiconductor using an atomically controlled ferromagnet/ferromagnet/semiconductor heterostructure with low-resistive Schottky-tunnel barriers. On the basis of symmetry matching of the electronic bands between the top highly spin-polarized ferromagnet and the semiconductor, the magnitude of the spin signals in lateral spin-valve devices can be enhanced by up to one order of magnitude compared to those obtained with conventional ferromagnet/semiconductor structures. This approach provides a new solution for the simultaneous achievement of highly efficient spin injection and low electric power at the electrodes in semiconductor devices, leading to novel semiconductor spintronic architectures at room temperature.

Highlights

Architectures based on the electron spin degree of freedom, electrical injection of spin-polarized electrons from a ferromagnetic material (FM), manipulation of the injected spins by applying magnetic fields, and electrical detection of the manipulated spins have been demonstrated in SC device structures[1,2]
Energy-band symmetry and spin-dependent transmittance Considering Fig. 1a, we hereinafter focus on the spindependent transport properties of electrons based on the band symmetry matching arguments for CFAS/Fe/Ge heterostructures
The value of the band gap for Ge is underestimated in our calculation conditions with the generalized gradient approximation (GGA), the conduction band symmetry can be precisely depicted

Summary

Introduction

For the achievement of novel semiconductor (SC)architectures based on the electron spin degree of freedom, electrical injection of spin-polarized electrons from a ferromagnetic material (FM), manipulation of the injected spins by applying magnetic fields, and electrical detection of the manipulated spins have been demonstrated in SC device structures[1,2]. We theoretically find that the CFAS/Fe5–6/Ge heterostructure along the direction has energyband symmetry matching, leading to efficient injection of spin-polarized electrons into the conduction band of Ge. In the CFAS/Fe5–6/Ge LSV devices, we can experimentally achieve a more than one order of magnitude enhancement in the MR ratio (∼0.04%) at room temperature and the lowest electric power (∼0.12 mW) for obtaining a high MR ratio. In the CFAS/Fe5–6/Ge LSV devices, we can experimentally achieve a more than one order of magnitude enhancement in the MR ratio (∼0.04%) at room temperature and the lowest electric power (∼0.12 mW) for obtaining a high MR ratio Given these novel findings, we can conclude that spin injection through symmetry matching of the electronic bands between the top highly spin-polarized FM and SC in FM/FM/SC heterostructures provides a new solution for the simultaneous achievement of highly efficient spin injection at room temperature and low electric power at the electrodes, leading to novel SC spintronic architectures

Methods

Results

Conclusion