10:00 〜 10:15
▲ [16a-501-4] Large Spin Polarization in Si and the Spin Diffusion term observed in Co2FeSi/MgO/n+-Si on Insulator devices
キーワード：Spin Injection/Detection, Hanle Measurements, Spin-MOSFET
In order to realize the Spin-MOSFET, highly efficient spin injection and detection in ferromagnetic metal (FM)/insulator (I)/semiconductor (S) junction are necessary. The efficiency of spin injection and detection depends on the spin polarization of the FM, the spin selectivity of the tunnel barrier, and the conductivity matching condition [1]. Our group has previously reported that Heusler alloy (Co2FeSi) shows better spin polarization as compared with CoFe ferromagnet on Si (1´1) surface [2]. Furthermore, on Si (2´1) surface, enhancement of spin injection efficiency in CoFe/MgO/n+-Si on insulator devices compared to the case on Si (1´1) surface was observed by our group [3].
In the present study, the 4-terminal devices with Co2FeSi/MgO electrodes on phosphorous-doped (~1.5×1019 cm-3) (100)-textured Si on insulator substrates were prepared on Si (2´1) surface and non-local 4-terminal and 3-terminal narrow Hanle signal were investigated at RT. The polarization at room temperature is ~ 42 %, estimated from 4-terminal Hanle measurement, as shown in Fig. 1 [4]. The spin transport lengths were also estimated from the 3-terminal Hanle fitting at each bias voltage. At Vbias = 0 (i.e. no drift effect) the spin diffusion length were estimated from 4-terminal non-local Hanle measurement. The spin transport length was fitted using the spin drift-diffusion equation [5]. It is obvious from Fig. 2, the spin transport length as function of bias voltage is nicely fitted using the spin drift-diffusion equation, for both temperatures 300 and 20 K. This indicates that the bias voltage dependence of the spin transport length can be explained by intruding the spin drift term.
This work was partly supported by the ImPACT Program of the Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
References
[1] A. Fert and H. Jaffrres, Phys. Rev. B 64, 184420 (2001), [2] M. Ishikawa, et al. Appl. Phys. Lett. 107, 092402 (2015), [3] M. Ishikawa et al. , Int. Conf. Sol. Stat. Mat. PS-12-18 (2015), [4] A. Tiwari et al. to be published in JJAP (2017), [5] M. Kameno et al. Appl. Phys. Lett. 104, 092409 (2014).
In the present study, the 4-terminal devices with Co2FeSi/MgO electrodes on phosphorous-doped (~1.5×1019 cm-3) (100)-textured Si on insulator substrates were prepared on Si (2´1) surface and non-local 4-terminal and 3-terminal narrow Hanle signal were investigated at RT. The polarization at room temperature is ~ 42 %, estimated from 4-terminal Hanle measurement, as shown in Fig. 1 [4]. The spin transport lengths were also estimated from the 3-terminal Hanle fitting at each bias voltage. At Vbias = 0 (i.e. no drift effect) the spin diffusion length were estimated from 4-terminal non-local Hanle measurement. The spin transport length was fitted using the spin drift-diffusion equation [5]. It is obvious from Fig. 2, the spin transport length as function of bias voltage is nicely fitted using the spin drift-diffusion equation, for both temperatures 300 and 20 K. This indicates that the bias voltage dependence of the spin transport length can be explained by intruding the spin drift term.
This work was partly supported by the ImPACT Program of the Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
References
[1] A. Fert and H. Jaffrres, Phys. Rev. B 64, 184420 (2001), [2] M. Ishikawa, et al. Appl. Phys. Lett. 107, 092402 (2015), [3] M. Ishikawa et al. , Int. Conf. Sol. Stat. Mat. PS-12-18 (2015), [4] A. Tiwari et al. to be published in JJAP (2017), [5] M. Kameno et al. Appl. Phys. Lett. 104, 092409 (2014).