Improved electrical properties of MoS2 transistor with Hf1-xTixO 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 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
₂
as 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
₂
to 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.