Effects of HfO2 encapsulation on electrical performances of few-layered MoS2 transistor with ALD HfO2 as back-gate dielectric
Effects of HfO2 encapsulation on electrical performances of few-layered MoS2 transistor with ALD HfO2 as back-gate dielectric
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HfO2 封装对 ALD HfO2 作为背栅介质的少层 MoS2 晶体管电性能的影响
DOI：
10.1088/1361-6528/aac853
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发表时间：
2018-06
期刊：
影响因子：
3.5
通讯作者：
Wing-Man Tang
中科院分区：
文献类型：
--
作者：
Jingping Xu;Ming Wen;Xinyuan Zhao;Lu Liu;Xingjuan Song;Pui-To Lai;Wing-Man Tang
高k栅介质的屏蔽作用可以大大提高MoS 2晶体管的载流子迁移率。采用原子层淀积（ALD）HfO 2代替SiO2作为栅介质，制备了背栅少层MoS 2晶体管，获得了良好的电学性能，其场效应迁移率（μ）为19.1 cm 2 V-1 s-1，亚阈值摆幅（SS）为123.6 mV dec-1，通断比（ON/OFF）为3.76 × 105。此外，当用具有不同厚度的ALD HfO 2层涂覆MoS 2沟道的表面时，获得增强的器件性能（10、15和20 nm），其中具有15 nm HfO 2封装层的晶体管表现出最佳的总体电性能：μ = 42.1 cm 2 V-1 s-1，SS = 87.9 mV dec-1，开/关比为2.72 × 106。这些改进应与增强的屏蔽效应的带电杂质散射和保护环境气体分子的吸收的高k封装。背栅介质（HfO 2）的电容等效厚度仅为6.58 nm，这有利于MoS 2晶体管的缩放。
The carrier mobility of MoS2 transistors can be greatly improved by the screening role of high-k gate dielectric. In this work, atomic-layer deposited (ALD) HfO2 annealed in NH3 is used to replace SiO2 as the gate dielectric to fabricate back-gated few-layered MoS2 transistors, and good electrical properties are achieved with field-effect mobility (μ) of 19.1 cm2 V–1 s–1, subthreshold swing (SS) of 123.6 mV dec–1 and on/off ratio of 3.76 × 105. Furthermore, enhanced device performance is obtained when the surface of the MoS2 channel is coated by an ALD HfO2 layer with different thicknesses (10, 15 and 20 nm), where the transistor with a 15 nm HfO2 encapsulation layer exhibits the best overall electrical properties: μ = 42.1 cm2 V–1 s–1, SS = 87.9 mV dec–1 and on/off ratio of 2.72 × 106. These improvements should be associated with the enhanced screening effect on charged-impurity scattering and protection from absorption of environmental gas molecules by the high-k encapsulation. The capacitance equivalent thickness of the back-gate dielectric (HfO2) is only 6.58 nm, which is conducive to scaling of the MoS2 transistors.
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