Performance tunability of field-effect transistors using MoS2(1- x)Se2 xalloys

Sooraj Sanjay; Kolla Lakshmi Ganapathi; Eswaraiah Varrla; Navakanta Bhat

doi:10.1088/1361-6528/ac1717

Performance tunability of field-effect transistors using MoS_{2(1- x)}Se_{2 x}alloys

Nanotechnology. 2021 Aug 6;32(43). doi: 10.1088/1361-6528/ac1717.

Authors

Sooraj Sanjay¹, Kolla Lakshmi Ganapathi², Eswaraiah Varrla³, Navakanta Bhat¹

Affiliations

¹ Centre for Nano Science and Engineering, Indian Institute of Science, Bengaluru - 560012, India.
² Department of Physics, 2D Materials Research and Innovation-group, Quantum Centers in Diamond and Emergent Materials (QuCenDiEM)-group, Indian Institute of Technology Madras, Chennai - 600036, India.
³ Laboratory of Nanosheets and Nanocomposites, Department of Physics and Nanotechnology, SRM Institute of Science and Technology, Kattankulathur, Chengalpattu, Tamil Nadu - 603202, India.

PMID: 34293721
DOI: 10.1088/1361-6528/ac1717

Abstract

Ultra-thin channel materials with excellent tunability of their electronic properties are necessary for the scaling of electronic devices. Two-dimensional materials such as transition metal dichalcogenides (TMDs) are ideal candidates for this due to their layered nature and great electrostatic control. Ternary alloys of these TMDs show composition-dependent electronic structure, promising excellent tunability of their properties. Here, we systematically compare molybdenum sulphoselenide (MoS₂₍_1-x₎Se_2x) alloys, MoS₁Se₁and MoS_0.4Se_1.6. We observe variations in strain and carrier concentration with their composition. Using them, we demonstrate n-channel field-effect transistors (FETs) with SiO₂and high-kHfO₂as gate dielectrics, and show tunability in threshold voltage, subthreshold slope (SS), drain current, and mobility. MoS₁Se₁shows better promise for low-power FETs with a minimum SS of 70 mV dec^-1, whereas MoS_0.4Se_1.6, with its higher mobility, is suitable for faster operations. Using HfO₂as gate dielectric, there is an order of magnitude reduction in interface traps and 2× improvement in mobility and drain current, compared to SiO₂. In contrast to MoS₂, the FETs on HfO₂also display enhancement-mode operation, making them better suited for CMOS applications.

Keywords: 2D alloys; FETs; HfO2; MoS2(1−x)Se2x; interfaces; tunability.