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 WS 2 and Er 3+ in situ doped WSe 2 are prepared by the chemical vapor deposition method. Thicknesses and atomic structures of the prepared WS 2 and WSe 2 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 Er 3+ doping concentration in WSe 2 are examined by energy dispersive spectroscopy and X‐ray photoelectron spectroscopy, respectively. Performances of photodetectors based on the WSe 2 and Er 3+ doped WSe 2 membranes are characterized individually. A microregion fixed‐point transfer technique is used to transfer the monolayer WS 2 onto the Er‐doped monolayer WSe 2 to form vertical van der Waals heterojunctions. Excellent performances are measured from the monolayer WS 2 /WSe 2 (Er 3+ ) 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 Er 3+ in situ doping in WS 2 /WSe 2 (Er) heterojunctions for high‐performance photodetectors.