Carrier‐Type Modulation and Mobility Improvement of Thin MoTe₂

Abstract A systematic modulation of the carrier type in molybdenum ditelluride (MoTe 2 ) field‐effect transistors (FETs) is described, through rapid thermal annealing (RTA) under a controlled O 2 environment (p‐type modulation) and benzyl viologen (BV) doping (n‐type modulation). Al 2 O 3 capping is then introduced to improve the carrier mobilities and device stability. MoTe 2 is found to be ultrasensitive to O 2 at elevated temperatures (250 °C). Charge carriers of MoTe 2 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 2 ‐transistor performance are confirmed to originate from the physical and chemical absorption and dissociation of O 2 , especially at tellurium vacancy sites. The electron branch is modulated by varying the BV dopant concentrations and annealing conditions. Unipolar n‐type MoTe 2 FETs with a high on–off ratio exceeding 10 6 are achieved under optimized doping conditions. By introducing Al 2 O 3 capping, carrier field effect mobilities (41 for holes and 80 cm 2 V −1 s −1 for electrons) and device stability are improved due to the reduced trap densities and isolation from ambient air. Lateral MoTe 2 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.

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