2D WS₂/WSe₂(Er) Heterojunction for High Performance Photodetectors

Abstract 2D transition metal dichalcogenides and their heterojunctions have demonstrated great potentialities for applications in optoelectronics, and rare‐earth doping has proven an effective way for achieving high performance. Here, 2D WS₂ and Er³⁺ in situ doped WSe₂ are prepared by the chemical vapor deposition method. Thicknesses and atomic structures of the prepared WS₂ and WSe₂ are characterized by atomic force microscopy and transmission electron microscope, while qualities of the membranes are characterized by photoluminescence spectroscopy and Raman spectroscopy, respectively. The 13.7 and 15.8 at% of Er³⁺ doping concentration in WSe₂ are examined by energy dispersive spectroscopy and X‐ray photoelectron spectroscopy, respectively. Performances of photodetectors based on the WSe₂ and Er³⁺ doped WSe₂ membranes are characterized individually. A microregion fixed‐point transfer technique is used to transfer the monolayer WS₂ onto the Er‐doped monolayer WSe₂ to form vertical van der Waals heterojunctions. Excellent performances are measured from the monolayer WS₂/WSe₂(Er³⁺) heterojunction photodetector with a photoresponsivity (R_λ) of up to 40.5 A W⁻¹ and external quantum efficiency (EQE) of 8793%. The results prove the effectiveness of Er³⁺ in situ doping in WS₂/WSe₂(Er) heterojunctions for high‐performance photodetectors.