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

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-lambda) 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.