Precisely controllable n-type doping in MoTe2 field effect transistors by hydrazine treatment

Abstract

An accurate and controllable n-type doping method for MoTe2 field effect transistors is developed by hydrazine treatment. It is shown that hydrazine molecules are absorbed physically without a new substance being formed, as determined by X-ray photoelectron spectroscopy measurements. The conduction type, electron concentrations, and minimum conductivity points in the transfer characteristics could be modulated precisely for a wide range by varying the concentration of hydrazine solution. Compared to pristine MoTe2 control devices, the electron concentrations are changed from 9.67 × 1011 cm−2 to 3.46 × 1012 cm−2 in the n-type regime, while the electron current on/off ratio is increased from 104 to 106 after 5 wt. % of hydrazine treatment. It is also interesting to observe that the ambipolar window increases almost linearly as the device temperature is reduced from 260 K to 5 K. The effective Schottky barrier heights for electrons in hydrazine treated MoTe2 field-effect transistors are extracted and found to be lower than 0.024 eV, indicating that the thermionic emission is not dominated. Furthermore, a lateral MoTe2 p–n junction with a rectification ratio higher than 103 and an ideality factor of around 1.66 is demonstrated through selective doping. This developed unique method of n-type doping and p-n junction creates an opportunity to fabricate high performance functional devices based on 2D layered materials.