p-type degenerate doping of 2H-MoTe₂

On-chip fiber optic communication systems require photodiodes and light emitting diodes which operate in the infrared (IR) / Near-infrared (NIR) regions. Among the different direct bandgap van der Waals semiconductors, monolayer Molybdenum Telluride (2H-phase) is an excellent candidate. 2H-MoTe₂ has a bandgap of 1.1 eV in the monolayer limit. However, this material is very air-sensitive and requires a passivation layer to operate in ambient conditions.

Here, in this work, we show a p-type degenerate doping of 2H-MoTe₂ using a monolayer of Tungsten Oxyselenide (TOS) – an amorphous, stable and high work-function oxide obtained by oxidation of WSe₂. We characterize the doping in MoTe₂ using Raman and electrical characterization that shows degenerate doping of MoTe₂ using TOS while simultaneuously acting as a passivation layer. We show work-function dependent charge-transfer simulations that indicate > 10¹³ cm^-2 doping density. In conclusion, we demonstrate a degenerate p-type doping technique to dope 2H-MoTe₂ which can be used to fabricate p-n junction.