Capacitance–voltage analysis of electrical properties for WSe2 field effect transistors with high-k encapsulation layer. (10th January 2018)

• Record Type: Journal Article
• Authors: Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho Kyun; You, Min Youl; Jin, Jun-Eon; Choi, Miri; Cho, Jiung; Kim, Gyu-Tae
• Is Part Of: Nanotechnology. Volume 29:Number 6(2018)
• Publication Date: 2018-01-10
• Subjects: WSe2 -- field effect transistors -- high-k encapsulation layer (Al2O3) -- Doping effects; Nanotechnology -- Periodicals; Nanotechnology -- Periodicals; Nanotechnology; Publications périodiques; Nanotechnologies; Periodicals; 620.5
• DOI: 10.1088/1361-6528/aaa1d7
• Languages: English
• ISSNs: 0957-4484

Abstract

Abstract: Doping effects in devices based on two-dimensional (2D) materials have been widely studied. However, detailed analysis and the mechanism of the doping effect caused by encapsulation layers has not been sufficiently explored. In this work, we present experimental studies on the n-doping effect in WSe2 field effect transistors (FETs) with a high-k encapsulation layer (Al2 O3 ) grown by atomic layer deposition. In addition, we demonstrate the mechanism and origin of the doping effect. After encapsulation of the Al2 O3 layer, the threshold voltage of the WSe2 FET negatively shifted with the increase of the on-current. The capacitance–voltage measurements of the metal insulator semiconductor (MIS) structure proved the presence of the positive fixed charges within the Al2 O3 layer. The flat-band voltage of the MIS structure of Au/Al2 O3 /SiO2 /Si was shifted toward the negative direction on account of the positive fixed charges in the Al2 O3 layer. Our results clearly revealed that the fixed charges in the Al2 O3 encapsulation layer modulated the Fermi energy level via the field effect. Moreover, these results possibly provide fundamental ideas and guidelines to design 2D materials FETs with high-performance and reliability.