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

Abstract

Carrier mobility of MoS 2transistor can be greatly improved by screening the Columbic scattering by a high-k gate dielectric. In this work, different TiO 2amounts are incorporated into HfO 2to form Hf 1-x Ti x O gate dielectrics to investigate its effects on the electrical properties of MoS 2transistor. It is found that enhanced carrier mobility and decreased gate leakage current can be achieved by optimizing the Ti content, i.e. with Hf 0.9 Ti 0.1 O (x = 0.1) as the gate dielectric, the device exhibits the highest carrier mobility of 31.5 cm 2 /Vs, which is 1.3× improvement as compared to the sample with HfO 2as gate dielectric (24.1 cm 2 /Vs). The main mechanism lies in that Hf 1-x Ti x O has higher k value than HfO 2to increase the Coulomb screening effect and thus carrier mobility. However, with further increase of Ti content, e.g. Hf 0.85 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 Hf 0.85 Ti 0.15 O and MoS 2 , and degraded MoS 2 /Hf 1-x Ti x O interface quality.