Carrier‐Type Modulation and Mobility Improvement of Thin MoTe₂

Abstract

A systematic modulation of the carrier type in molybdenum ditelluride (MoTe ) field-effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O environment (p-type modulation) and benzyl viologen (BV) doping (n-type modulation). Al O capping is then introduced to improve the carrier mobilities and device stability. MoTe is found to be ultrasensitive to O at elevated temperatures (250 °C). Charge carriers of MoTe flakes annealed via RTA at various vacuum levels are tuned between predominantly pristine n-type ambipolar, symmetric ambipolar, unipolar p-type, and degenerate-like p-type. Changes in the MoTe -transistor performance are confirmed to originate from the physical and chemical absorption and dissociation of O , especially at tellurium vacancy sites. The electron branch is modulated by varying the BV dopant concentrations and annealing conditions. Unipolar n-type MoTe FETs with a high on-off ratio exceeding 10 are achieved under optimized doping conditions. By introducing Al O capping, carrier field effect mobilities (41 for holes and 80 cm V s for electrons) and device stability are improved due to the reduced trap densities and isolation from ambient air. Lateral MoTe p-n diodes with an ideality factor of 1.2 are fabricated using the p- and n-type doping technique to test the superb potential of the doping method in functional electronic device applications.

Atomic Vacancy Control and Elemental Substitution in a Monolayer Molybdenum Disulfide for High Performance Optoelectronic Device Arrays

“…Seo et al employed a focused laser beam to manipulate the defects in molybdenum ditelluride (MoTe 2 ) multilayers and fabricated large‐area integrated circuits composed of bipolar junction transistors and photovoltaic cells . Nonetheless, this approach is limited to a specific TMDC material, in this case, MoTe 2 , which has a negligible Fermi level pinning effect compared to other 2D TMDCs (i.e., MoS 2 and tungsten diselenide, WSe 2 ) . Furthermore, as mentioned above, the majority of defect engineering studies have been performed on multilayers of TMDCs, whereas there exist only few reports on the defect engineering of a TMDC monolayer, which is favorable for optical device applications thanks to its direct bandgap in most cases and has the higher feasibility for large‐area growth.…”

“…Nonetheless, this approach is limited to a specific TMDC material, in this case, MoTe 2 , which has a negligible Fermi level pinning effect compared to other 2D TMDCs (i.e., MoS 2 and tungsten diselenide, WSe 2 ) . Furthermore, as mentioned above, the majority of defect engineering studies have been performed on multilayers of TMDCs, whereas there exist only few reports on the defect engineering of a TMDC monolayer, which is favorable for optical device applications thanks to its direct bandgap in most cases and has the higher feasibility for large‐area growth. However, the defect engineering of a monolayer requires very specialized experimental conditions to minimize the structural damage .…”

Controllable P‐ and N‐Type Conversion of MoTe2 via Oxide Interfacial Layer for Logic Circuits

“…2H‐MoTe 2 , which is a representative 2D‐TMDC and possesses a band gap of 0.9 and 1.1 eV in bulk and monolayer form, respectively, has recently been recognized as a potential candidate for its utility in high‐tunneling current tunnel field‐effect transistors (TFETs) . MoTe 2 exhibits p‐type characteristics owing to the adsorption of O 2 on the surface from the ambient; therefore, it could be relatively easy to convert MoTe 2 into n‐type via surface doping . At the same time, the reduction of the Schottky barrier height can be expected via the insertion of an insulating layer at the interface between MoTe 2 and metal.…”

High‐Electric‐Field‐Induced Phase Transition and Electrical Breakdown of MoTe2

“…Power dissipation in 2D materials, including graphene, black phosphorus, and other TMDCs, has been studied by Raman spectroscopy under the high electrical fields applied to the FET structure 11,13–16. To the best of our knowledge, the power dissipation and electrical breakdown of molybdenum ditelluride (MoTe 2 ) have not been studied intensively, although it is one of the most promising TMDCs that can be employed for future 2D device applications requiring ambipolar semiconducting properties 17–20. MoTe 2 is known to have a 2H semiconducting phase with the thickness dependent band gap in the range from 0.83 to 1.1 eV 21,22.…”