Top-gated chemical vapor deposited MoS₂ field-effect transistors on Si₃N₄ substrates

We report the electrical characteristics of chemical vapor deposited (CVD) monolayer molybdenum disulfide (MoS₂) top-gated field-effect transistors (FETs) on silicon nitride (Si₃N₄) substrates. We show that Si₃N₄ substrates offer comparable electrical performance to thermally grown SiO₂ substrates for MoS₂ FETs, offering an attractive passivating substrate for transition-metal dichalcogenides (TMD) with a smooth surface morphology. Single-crystal MoS₂ grains are grown via vapor transport process using solid precursors directly on low pressure CVD Si₃N₄, eliminating the need for transfer processes which degrade electrical performance. Monolayer top-gated MoS₂ FETs with Al₂O₃ gate dielectric on Si₃N₄ achieve a room temperature mobility of 24 cm²/V s with I_on/I_off current ratios exceeding 10⁷. Using HfO₂ as a gate dielectric, monolayer top-gated CVD MoS₂ FETs on Si₃N₄ achieve current densities of 55 μA/μm and a transconductance of 6.12 μS/μm at V_tg of −5 V and V_ds of 2 V. We observe an increase in mobility at lower temperatures, indicating phonon scattering may dominate over charged impurity scattering in our devices. Our results show that Si₃N₄ is an attractive alternative to thermally grown SiO₂ substrate for TMD FETs.