Unlocking performance potential of two-dimensional SnS₂ transistors with solution-processed high-k Y:HfO₂ film and semimetal bismuth contact

Two-dimensional (2D) tin disulfide (SnS₂) is emerging as a viable channel material for high-performance field-effect transistors (FET) with high intrinsic mobility. To implement a high-performance two-dimensional SnS₂ FET, high field-effect mobility (μ_FE), steep subthreshold swing (SS), high on-current value (I_on), and high on/off ratio (I_on/I_off) must be realized. To improve these parameters, we first fabricated a high-k (∼30.5) yttrium-doped hafnium dioxide (Y:HfO₂) film through a solution process to suppress Coulomb electron scattering, and to enhance the semiconductor-dielectric interface with an efficient metal–oxygen framework and a very smooth (root mean square = 0.29 nm) surface. Second, we induced Fermi level depinning by introducing a semimetal bismuth (Bi) contact with a low density of states (DOS) at the Fermi level to suppress the metal-induced gap state (MIGS). Through these two strategies, the SnS₂ FET obtained high μ_FE (60.5 cm²V^-1s⁻¹), the SS theoretical limit of 60 mV/dec, negligible Schottky barrier height, high normalized on-current (I_onL/W) of 90.6 μA, and high I_on/I_off of 3 × 10⁷, demonstrating that SnS₂ can be re-evaluated as a potentially effective 2D channel material.