Enhanced Mobility Of MoS₂ Field-Effect Transistors Via Surface Passivation

With the decreasing feature size of semiconductor devices,MoS₂ is considered to have the potential as the channel material of the next generation nano-electronic devices due to its excellent electrical properties.Although the research on MoS₂ FETs(Field-Effect Transistors)has made some progress,the carrier mobility of the device is still far from its intrinsic limit,which limits the application of MoS₂ in high-performance semiconductor devices.Therefore,this paper focuses on improving the mobility of MoS₂ FETs.Experimentally,SiO₂ was used as the gate dielectric and MoS₂ was vulcanized at 150,200 and 250?to fabricate MoS₂ FETs.The measurement of electrical characteristics showed that the 200?vulcanization treatment can most effectively repair the S vacancies and increase the carrier mobility.On this basis,when Hf O₂ and Al₂O₃ were used to replace SiO₂ and MoS₂ was vulcanized at 200?to fabricate MoS₂ FETs,it was found that the mobility of transistors with Al₂O₃ as the gate dielectric was further improved,reaching 64.74cm²/Vs.These are mainly attributed to the fact that a suitable k-value of Al₂O₃ can produce a dominant dielectric-screening effect overwhelming the phonon scattering,increasing the carrier mobility,while larger k-value of Hf O₂ will enhance the phonon scattering to counteract the dielectric-screening effect.Furthermore,Al₂O₃ was used as the gate dielectric and MoS₂ was treated with 20,30 and 40 W power oxygen plasma at room temperature to fabricate MoS₂ FETs.It was found that 30 W oxygen plasma can most effectively fill the S vacancies in MoS₂,reduce the scattering center,and increase the carrier mobility to 69.82cm²/Vs,while high power plasma will destroy the lattice structure of MoS₂,resulting in the decrease of mobility.Theoretically,first-principles method was used to calculate the carrier mobility of intrinsic and single-layer MoS₂ with S vacancies.The results showed that with the introduction of S vacancy,MoS₂ transformed from the intrinsic direct band gap to the indirect band gap.In addition,the elastic modulus of MoS₂ was reduced,the deformation potential constant and effective mass of electrons and holes were increased,which leaded to the decrease in the carrier mobility of MoS₂.The theoretical calculation provides a theoretical basis for the experimental results of surface passivation to improve the mobility of MoS₂transistors.