Improved electrical properties of MoS2 transistor with Hf1-xTixO as gate dielectric

Carrier mobility of MoS2 transistor can be greatly improved by screening the Columbic scattering by a high-k gate dielectric. In this work, different TiO2 amounts are incorporated into HfO2 to form Hf1-xTixO gate dielectrics to investigate its effects on the electrical properties of MoS2 transistor. It is found that enhanced carrier mobility and decreased gate leakage current can be achieved by optimizing the Ti content, i.e. with ${\rm{Hf}}_{0.9}{\rm{Ti}}_{0.1}O (x\ =\ 0.1)$ as the gate dielectric, the device exhibits the highest carrier mobility of 31.5 ${\rm{cm}}^{2}/Vs$, which is $ 1.3\times$ improvement as compared to the sample with HfO2 as gate dielectric $(24.1\ {\rm{cm}}^{2}/Vs)$. The main mechanism lies in that Hf1-xTixO has higher k value than HfO2 to increase the Coulomb screening effect and thus carrier mobility. However, with further increase of Ti content, e.g. ${\rm{Hf}}_{0.85}{\rm{Ti}}_{0.15}O (x=\ 0.15)$, the device exhibits larger off current and degraded subthreshold swing. This is probably attributed to Ti-related oxide traps, a decreased conduction-band offset between ${\rm{Hf}}_{0.85}{\rm{Ti}}_{0.15}{\rm{O}}$ and MoS2, and degraded $MoS_{2}/{\rm{Hf}}_{1-x}{\rm{Ti}}_{x}{\rm{O}}$ interface quality.