Enhancement of the Spin-Orbit Coupling in Silicon by Bismuth Doping

Si possesses a low spin-orbit coupling, it allows a long spin lifetime but limits new device-designing possibilities in spintronics, particularly with the spin-charge conversion effects to create an all-Si spin devices. The purpose of this study is to create a sizable spin-orbit interaction in Si by implantation of a heavy element, bismuth (Bi).
To compare the spin-orbit coupling strength in the Si channel with and without Bi doping (SOI:P:B and SOI:P, respectively), we measured quantum corrections to the conductance in function of temperature. The elastic diffusion length (L_e), the spin-orbit coupling length (L_so) and the phase coherence length (L_φ) can be extracted from the magnetoconductance data by using the Hikami-Larkin-Nagaoka model. L_e has the same order of magnitude (10 nm-25 nm) for both samples, however L_φ decreased after the Bi doping (with the strongest decrease from 177 nm to 35 nm at 2 K). In the case of SOI:P:Bi, the Bi doping induced a spin-orbit coupling length of the same order of magnitude with the phase coherence length (L_so= 54 nm and L_φ= 35 nm at 2K).
The increased spin-orbit coupling strength led to observe the crossover between the WL and the WAL. These results demonstrate a control over the strength of the spin-orbit coupling in Si channel using Bi doping.