P-GaSe/N-MoS₂ Vertical Heterostructures Synthesized by van der Waals Epitaxy for Photoresponse Modulation

The important role of p-n junction in modulation of the optoelectronic properties of semiconductors is widely cognized. In this work, for the first time the synthesis of p-GaSe/n-MoS₂ heterostructures via van der Waals expitaxial growth is reported, although a considerable lattice mismatching of ≈18% exists. According to the simulation, a significant type II p-n junction barrier located at the interface is expected to be formed, which can modulate optoelectronic properties of MoS₂ effectively. It is intriguing to reveal that the presence of GaSe can result in obvious Raman and photoluminescence (PL) shift of MoS₂ compared to that of pristine one, more interestingly, for PL peak shift, the effect of GaSe-induced tensile strain on MoS₂ has overcome the p-doping effect of GaSe, evidencing the strong interlayer coupling between GaSe and MoS₂ . As a result, the photoresponse rate of heterostructures is improved by almost three orders of magnitude compared with that of pristine MoS₂ .