High-Performance HfO2 Back Gated Multilayer MoS2 Transistors

A new substrate (~30-nm HfO₂/Si) is developed for high-performance back-gated molybdenum disulfide (MoS₂) transistors. Record drain current I_ds~180 μA/μm and transconductance value g_m~75 μS/μm at V_ds = 1V have been achieved for 1-μm channel length multilayer MoS₂ transistors on HfO₂/Si substrate. The transistors on HfO₂ substrate show > 2.5× enhancement in field effect mobility (μ_FE~65 cm²/V·s) compared with the transistors on SiO₂ (μ_FE~65 cm²/V·s) substrate. The intrinsic mobility extracted from Y function technique (μ_FE~154 cm²/V·s) is 3× more than SiO₂ substrate. The drastic improvement in transistor performance is attributed to a combination of three factors: 1) efficient gate coupling with an EOT of 6.2 nm; 2) charge impurity screening due to high-k dielectric; and 3) very low contact resistance through sulfur treatment.