MoS₂ Transistors with 4 nm hBN Gate Dielectric and 0.46 V Threshold Voltage

The use of two-dimensional (2D) semiconducting materials (MoS₂, WS₂) as a channel in field-effect transistors may help extend Moore's law and produce devices beyond the complementary metal-oxide-semiconductor (CMOS) technology. Traditional dielectrics used in microelectronics (SiO₂, HfO₂, Al₂O₃) form a defective interface with the 2D semiconductor─because the latter does not have dangling bonds─leading to multiple device reliability issues and premature failure. Using 2D hexagonal boron nitride (hBN) as the gate dielectric sounds like a potential solution because it can form a clean van der Waals interface with the 2D semiconductor. However, its relative permittivity is only 3.6, which has raised concerns: it is believed that a MoS₂ transistor with hBN gate dielectric cannot be switched ON without the apparition of gate leakage current. Here, we show that transistors with a Pt/4 nm-hBN/MoS₂ vertical structure can exhibit ON/OFF current ratios above 10⁵, low threshold voltage of 0.46 V, and low gate leakage current density (<i>J</i>_G) of 10^-4 A/cm². Moreover, our Pt/hBN/MoS₂ transistors show acceptable performance even after 1000 switching cycles: ON/OFF current ratio is above 10⁴ and <i>J</i>_G below 10^-4 A/cm². Our study indicates that hBN may be a suitable gate dielectric for some types of nanosized MoS₂ transistors.