High-Performance Transition Metal Dichalcogenide Photodetectors Enhanced by Self-Assembled Monolayer Doping

Most doping research into transition metal dichalcogenides (TMDs) has been mainly focused on the improvement of electronic device performance. Here, the effect of self-assembled monolayer (SAM)-based doping on the performance of WSe₂- and MoS₂-based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10¹¹ for octadecyltrichlorosilane (OTS) p-doping and ≈10¹¹ for aminopropyltriethoxysilane (APTES) n-doping (nondegenerate). Using this SAM doping technique, the field-effect mobility is increased from 32.58 to 168.9 cm² V^-1 s in OTS/WSe₂ transistors and from 28.75 to 142.2 cm² V^-1 s in APTES/MoS₂ transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10⁴ A W^-1) in the OTS/WSe₂ devices and by a factor of ≈26.4 (from 219 to 5.75 × 10³ A W^-1) in the APTES/MoS₂ devices. The enhanced photoresponsivity values are much higher than that of the previously reported TMD photodetectors. The detectivity enhancement is ≈26.6-fold in the OTS/WSe₂ devices and ≈24.5-fold in the APTES/MoS₂ devices and is caused by the increased photocurrent and maintained dark current after doping. The optoelectronic performance is also investigated with different optical powers and the air-exposure times. This doping study performed on TMD devices will play a significant role for optimizing the performance of future TMD-based electronic/optoelectronic applications.