Unlocking performance potential of two-dimensional SnS<sub>2</sub> transistors with solution-processed high-k Y:HfO<sub>2</sub> film and semimetal bismuth contact

Abstract

Two-dimensional (2D) tin disulfide (SnS2) is emerging as a viable channel material for high-performance fieldeffect transistors (FET) with high intrinsic mobility. To implement a high-performance two-dimensional SnS2 FET, high field-effect mobility (mu FE), steep subthreshold swing (SS), high on-current value (Ion), and high on/off ratio (I-on/I-off) must be realized. To improve these parameters, we first fabricated a high-k (similar to 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 mu FE (60.5 cm(2)V(-1)s(-1)), the SS theoretical limit of 60 mV/dec, negligible Schottky barrier height, high normalized on-current (IonL/W) of 90.6 mu A, and high I-on/ I-off of 3 x 10(7), demonstrating that SnS2 can be re-evaluated as a potentially effective 2D channel material.