Atomic layer deposited Al <sub>2</sub> O <sub>3</sub> passivation layer for few-layer WS <sub>2</sub> field effect transistors
Young Gyu You, Dong Ho Shin, Jong Hwa Ryu, E. E. B. Campbell, Hyun‐Jong Chung, Sung Ho Jhang
Abstract
Abstract We have investigated the effect of an Al 2 O 3 passivation layer on the performance of few-layer WS 2 FETs. While the performance of WS 2 FETs is often limited by a substantial decrease in carrier mobility owing to charged impurities and a Schottky barrier between the WS 2 and metal electrodes, the introduction of an Al 2 O 3 overlayer by atomic layer deposition (ALD) suppressed the influence of charged impurities by high- κ dielectric screening effect and reduced the effective Schottky barrier height. We argue that n-doping of WS 2 , induced by positive fixed charges formed at Al 2 O 3 /WS 2 interface during the ALD process, is responsible for the reduction of the effective Schottky barrier height in the devices. In addition, the Al 2 O 3 passivation layer protected the device from oxidation, and maintained stable electrical performance of the WS 2 FETs over 57 d. Thus, the ALD of Al 2 O 3 overlayer provides a facile method to enhance the performance of WS 2 FETs and to ensure ambient stability.