Improved electrical properties of MoS 2 transistor with Hf 1-x Ti x O as gate dielectric

Carrier mobility of MoS 2 transistor can be greatly improved by screening the Columbic scattering by a high-k gate dielectric. In this work, different TiO 2 amounts are incorporated into HfO 2 to form Hf 1-x Ti x O gate dielectrics to investigate its effects on the electrical properties of MoS 2 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 HfO 2 as gate dielectric $(24.1\ {\rm{cm}}^{2}/Vs)$. The main mechanism lies in that Hf 1-x Ti x O has higher k value than HfO 2 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 MoS 2 , and degraded $MoS_{2}/{\rm{Hf}}_{1-x}{\rm{Ti}}_{x}{\rm{O}}$ interface quality.