Enhancement of photodetection characteristics of MoS₂ field effect transistors using surface treatment with copper phthalocyanine

Recently, two-dimensional materials such as molybdenum disulfide (MoS₂) have been extensively studied as channel materials for field effect transistors (FETs) because MoS₂ has outstanding electrical properties such as a low subthreshold swing value, a high on/off ratio, and good carrier mobility. In this study, we characterized the electrical and photo-responsive properties of MoS₂ FET when stacking a p-type organic copper phthalocyanine (CuPc) layer on the MoS₂ surface. We observed that the threshold voltage of MoS₂ FET could be controlled by stacking the CuPc layers due to a charge transfer phenomenon at the interface. Particularly, we demonstrated that CuPc/MoS₂ hybrid devices exhibited high performance as a photodetector compared with the pristine MoS₂ FETs, caused by more electron-hole pairs separation at the p-n interface. Furthermore, we found the optimized CuPc thickness (∼2 nm) on the MoS₂ surface for the best performance as a photodetector with a photoresponsivity of ∼1.98 A W^-1, a detectivity of ∼6.11 × 10¹⁰ Jones, and an external quantum efficiency of ∼12.57%. Our study suggests that the MoS₂ vertical hybrid structure with organic material can be promising as efficient photodetecting devices and optoelectronic circuits.