Bias dependence of spin accumulation voltage in a non-degenerate Si spin valve

Si spintronics attracts great attention, and recent achievements in the field, such as the room temperature (RT) operation of spin MOSFET and the output spin voltage of more than 1 mV at RT due to the spin drift effect [1, 2], have been done by using non-degenerate (ND) Si. In the previous research [2], the spin voltages exhibited saturation under a high electric current (I_inj) injection regime, suggesting a possibility of modification of spin transport properties in the ND Si. Hence, we clarified the origin of the I_inj dependence of the spin signals in the ND Si in this study. The non-local 4-terminal measurement and the Hall measurement revealed that spin lifetime of the ND Si channel were independent of the I_inj at RT. Meanwhile, interface resistance of Fe/MgO/Si contact was reduced to the same order of spin resistance of the Si channel. A model calculation considering these results nicely reproduced the experimental I_inj dependence [3]. The detail will be discussed in the presentation.
[1] T. Tahara, Y. Ando, M. Shiraishi et al., Appl. Phys. Express 8, 113004 (2015).
[2] T. Tahara, Y. Ando, M. Shiraishi et al., Phys. Rev. B 93, 214406 (2016).
[3] S. Lee, Y. Ando, M. Shiraishi et al., submitted.