Bipolar magnetic semiconductor of 2D Janus Cr₂Ge₂Te₃Se₃ and its application in spin-FET

Two-dimensional (2D) Janus magnets exhibit a broad range of exotic physical phenomena, e.g. skyrmions and strong Rashba SOC, and become an important category of spintronic materials. Here, we design the Janus structure Cr₂Ge₂Te₃Se₃ based on the unipolar magnetic semiconductor (UMS) Cr₂Ge₂Te₆, and find that Cr₂Ge₂Te₃Se₃ becomes a bipolar magnetic semiconductor (BMS), whose valence band maximum (VBM) and conduction band minimum (CBM) have opposite spin polarization. The transition from UMS Cr₂Ge₂Te₆ to BMS Cr₂Ge₂Te₃Se₃ is achieved because the VBM is contributed by electronic states of the Se and Te atoms, which can be effectively modified by the mirror symmetry breaking. We then design a spin field-effect transistor (FET) based on Cr₂Ge₂Te₃Se₃, and demonstrate the half-metallic current tuned by the gate and bias voltages, through non-equilibrium Green's function theory. Our investigation schemes a 2D BMS and simulates its application in spin-FET, which potentially contributes to the development of 2D spintronic materials and devices.