Dielectric Engineering for Enhanced Top gate Monolayer MoS2 Transistor Using iCVD-based High-k Dielectric

Abstract

Transition metal chalcogen compounds have high transparency, flexibility, and excellent electrical properties. Among them, molybdenum disulfide(MoS2) is widely used as an n-type semiconductor material. In the case of MoS2, it has a relatively high on-off current ratio, high mobility, and excellent flexibility. However, It shows significantly lower mobility characteristics than its electrical potential because of its poor interfacial characteristic with an insulating layer and a substrate.[1] Particularly, because 2D materials have incongruity with a conventional ALD process due to their dangling bond free surface, 2D materials based transistors generally show inferior interface quality when they are applied in a form of top gate transistor.[2] In this study, by applying a newly invented initiated chemical deposition(iCVD) process based high-k dielectric(pHEMA-g-AlOX) as a top gate insulator of MoS2 transistor, high performance top gate monolayer MoS2 transistor with mobility of 13cm2V-1s-1, SS of 135mVdec-1 and low hysteresis(<100mV) value is developed.[3] Furthermore, it shows more than 5-times higher mobility than a conventional Al2O3 insulator-based top gate monolayer MoS2 transistor. Systematic analyses show the reason for this improvement is due to a less coulombic scattering effect and a less surface optical phonon scattering effect of a hybrid dielectric-based top gate MoS2 transistor than those of Al2O3 dielectric-based top gate device.