Integration of high-κ native oxides of gallium for two-dimensional transistors

The deposition of a metal oxide layer with good dielectric properties is a critical step in fabricating the gate dielectric of transistors based on two-dimensional semiconductors. However, current techniques for depositing ultrathin metal oxide layers on two-dimensional semiconductors suffer from quality issues that can compromise transistor performance. Here, we show that an ultrathin and uniform native oxide of gallium (Ga₂O₃) that naturally forms on the surface of liquid metals in an ambient environment can be prepared on the surface of molybdenum disulfide (MoS₂) by squeeze-printing and surface-tension-driven methods. The Ga₂O₃ layer possesses a high dielectric constant of around 30 and equivalent oxide thickness of around 0.4 nm. Due to the good dielectric properties and van der Waals integration, MoS₂ transistors with Ga₂O₃ gate dielectrics exhibit a subthreshold swing down to 60 mV dec⁻¹, an on/off ratio of 10⁸ and a gate leakage down to around 4 × 10⁻⁷ A cm⁻².