Improved performance of back-gate MoS₂ transistors by NH₃-plasma treating high-k gate dielectrics

NH₃-plasma treatment is used to improve the quality of the gate dielectric and interface. Al₂O₃ is adopted as a buffer layer between HfO₂ and MoS₂ to decrease the interface-state density. Four groups of MOS capacitors and back-gate transistors with different gate dielectrics are fabricated and their C-V and I-V characteristics are compared. It is found that the Al₂O₃/HfO₂ back-gate transistor with NH₃-plasma treatment shows the best electrical performance:high on-off current ratio of 1.53×10⁷, higher field-effect mobility of 26.51 cm²/V…, and lower subthreshold swing of 145 mV/dec. These are attributed to the improvements of the gate dielectric and interface qualities by the NH₃-plasma treatment and the addition of Al₂O₃ as a buffer layer.