Chemical vapor deposition of monolayer MoS2 directly on ultrathin Al2O3 for low-power electronics

Abstract

Monolayer MoS2 has recently been identified as a promising material for high-performance electronics. However, monolayer MoS2 must be integrated with ultrathin high-κ gate dielectrics in order to realize practical low-power devices. In this letter, we report the chemical vapor deposition (CVD) of monolayer MoS2 directly on 20 nm thick Al2O3 grown by atomic layer deposition (ALD). The quality of the resulting MoS2 is characterized by a comprehensive set of microscopic and spectroscopic techniques. Furthermore, a low-temperature (200 °C) Al2O3 ALD process is developed that maintains dielectric integrity following the high-temperature CVD of MoS2 (800 °C). Field-effect transistors (FETs) derived from these MoS2/Al2O3 stacks show minimal hysteresis with a sub-threshold swing as low as ∼220 mV/decade, threshold voltages of ∼2 V, and current ION/IOFF ratio as high as ∼104, where IOFF is defined as the current at zero gate voltage as is customary for determining power consumption in complementary logic circuits. The system presented here concurrently optimizes multiple low-power electronics figures of merit while providing a transfer-free method of integrating monolayer MoS2 with ultrathin high-κ dielectrics, thus enabling a scalable pathway for enhancement-mode FETs for low-power applications.