Carrier Type Control of WSe2 Field‐Effect Transistors by Thickness Modulation and MoO3 Layer Doping. (13th April 2016)

• Record Type: Journal Article
• Authors: Zhou, Changjian; Zhao, Yuda; Raju, Salahuddin; Wang, Yi; Lin, Ziyuan; Chan, Mansun; Chai, Yang
• Is Part Of: Advanced functional materials. Volume 26:Number 23(2016)
• Page Start: 4223
• Page End: 4230
• Publication Date: 2016-04-13
• Subjects: 2D materials -- carrier type -- doping -- field‐effect transistor; Materials -- Periodicals; Chemical vapor deposition -- Periodicals; 620.11
• DOI: 10.1002/adfm.201600292
• Languages: English
• ISSNs: 1616-301X

Abstract

Abstract : Control of the carrier type in 2D materials is critical for realizing complementary logic computation. Carrier type control in WSe2 field‐effect transistors (FETs) is presented via thickness engineering and solid‐state oxide doping, which are compatible with state‐of‐the‐art integrated circuit (IC) processing. It is found that the carrier type of WSe2 FETs evolves with its thickness, namely, p‐type (<4 nm), ambipolar (≈6 nm), and n‐type (>15 nm). This layer‐dependent carrier type can be understood as a result of drastic change of the band edge of WSe2 as a function of the thickness and their band offsets to the metal contacts. The strong carrier type tuning by solid‐state oxide doping is also demonstrated, in which ambipolar characteristics of WSe2 FETs are converted into pure p‐type, and the field‐effect hole mobility is enhanced by two orders of magnitude. The studies not only provide IC‐compatible processing method to control the carrier type in 2D semiconductor, but also enable to build functional devices, such as, a tunable diode formed with an asymmetrical‐thick WSe2 flake for fast photodetectors. Abstract : In the thickness‐dependent transport behavior of WSe2 transistors, it is revealed that all p‐type, ambipolar, and n‐type characteristics are obtained by merely varying the thickness of WSe2 flakes. The layer‐dependent band structure is a determining factor in achieving this strong thickness‐dependent transport behavior in WSe2 field‐effect transistors. The unique band structure of WSe2 also enables efficient p‐type doping in WSe2 by solid‐state oxide.