  A recent 2D spinFET concept proposes to switch electrostatically between two
separate sublayers with strong and opposite intrinsic Rashba effects. This
concept exploits the spin-layer locking mechanism present in centrosymmetric
materials with local dipole fields, where a weak electric field can easily
manipulate just one of the spin channels. Here, we propose a novel monolayer
material within this family, lutetium oxide iodide (LuIO). It displays one of
the largest Rashba effects among 2D materials (up to $k_R = 0.08$
{\AA}$^{-1}$), leading to a $\pi/2$ rotation of the spins over just 1 nm. The
monolayer had been predicted to be exfoliable from its experimentally-known 3D
bulk counterpart, with a binding energy even lower than graphene. We
characterize and model with first-principles simulations the interplay of the
two gate-controlled parameters for such devices: doping and spin channel
selection. We show that the ability to split the spin channels in energy
diminishes with doping, leading to specific gate-operation guidelines that can
apply to all devices based on spin-layer locking.
