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 (μFE), steep subthreshold swing (SS), high on-current value (Ion), and high on/off ratio (Ion/Ioff) 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 μFE (60.5 cm2V-1s−1), the SS theoretical limit of 60 mV/dec, negligible Schottky barrier height, high normalized on-current (IonL/W) of 90.6 μA, and high Ion/Ioff of 3 × 107, demonstrating that SnS2 can be re-evaluated as a potentially effective 2D channel material.