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

Abstract

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 WSe 2 ‐ and MoS 2 ‐based transistors and photodetectors is investigated. The achieved doping concentrations are ≈1.4 × 10 11 for octadecyltrichlorosilane (OTS) p‐doping and ≈10 11 for aminopropyltriethoxysilane (APTES) n‐doping (nondegenerate). Using this SAM doping technique, the field‐effect mobility is increased from 32.58 to 168.9 cm 2 V −1 s in OTS/WSe 2 transistors and from 28.75 to 142.2 cm 2 V −1 s in APTES/MoS 2 transistors. For the photodetectors, the responsivity is improved by a factor of ≈28.2 (from 517.2 to 1.45 × 10 4 A W −1 ) in the OTS/WSe 2 devices and by a factor of ≈26.4 (from 219 to 5.75 × 10 3 A W −1 ) in the APTES/MoS 2 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/WSe 2 devices and ≈24.5‐fold in the APTES/MoS 2 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.