Enhanced mobility of MoS₂ field-effect transistors by combining defect passivation with dielectric-screening effect

A facile method of combining the defect engineering with the dielectric-screening effect is proposed to improve the electrical performance of MoS₂ transistors. It is found that the carrier mobility of the transistor after the sulfur treatment on the MoS₂ channel is greatly enhanced due to the reduction of the sulfur vacancies during vulcanization of MoS₂. Furthermore, as compared to those transistors with HfO₂ and SiO₂ as the gate dielectric, the Al₂O₃-gate dielectric MoS₂ FET shows a better electrical performance after the sulfur treatment, with a lowered subthreshold swing of 179.4 mV/dec, an increased on/off ratio of 2.11 × 10⁶, and an enhanced carrier mobility of 64.74 cm²/Vs (about twice increase relative to the non-treated MoS₂ transistor with SiO₂ as the gate dielectric). These are mainly attributed to the fact that a suitable k-value gate dielectric can produce a dominant dielectric-screening effect overwhelming the phonon scattering, increasing the carrier mobility, while a larger k-value gate dielectric will enhance the phonon scattering to counteract the dielectric-screening effect, reducing the carrier mobility.