Proposed Nanoscale Spin Field-Effect Transistors with 2D Ferroelectric Rashba Semiconductors

The spin field-effect transistor (SFET) based on ferroelectric Rashba semiconductor (FRS) has a shorter channel length than ordinary transistors, making it an important type of future transistor. Through high-throughput inverse design, AlBi and SiPb monolayers are considered to be very promising FRSs due to their prominent Rashba effect, the thinnest atomic structure, and surmountable energy barriers. Herein, we employ first-principles calculations to systematically investigate the modulation of Rashba effect, electric field response, and ferroelectricity in AlBi and SiPb monolayers. The large Rashba coefficients of 2.717 and 2.606 eV·Å are obtained for AlBi and SiPb monolayers, while they can be efficiently modulated by the external electric field and strain engineering. The electric field response of AlBi oscillates around 0.5 e·Å² and that of SiPb can reach 0.78 e·Å², which can fully meet the requirements of practical applications. Furthermore, as typical two-dimensional ferroelectric materials, the coupling effect between ferroelectric polarization and spin polarization is also explored. Based on these investigations, we design two types of SFET with AlBi or SiPb monolayer as the channel. The SFET designed solely based on the electric field response without considering the ferroelectricity, has a channel length ranging from 70 nm to 100 nm. The SFET designed based on the ferroelectricity can reduce the channel length to below 2 nm, which is quite below the tolerance of coherent transport in semiconductors. Thus, two-dimensional (2D) FRS can be considered as a promising candidate material for the next generation of SFETs.