P-GaSe/N-MoS 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-MoS 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 MoS effectively. It is intriguing to reveal that the presence of GaSe can result in obvious Raman and photoluminescence (PL) shift of MoS compared to that of pristine one, more interestingly, for PL peak shift, the effect of GaSe-induced tensile strain on MoS has overcome the p-doping effect of GaSe, evidencing the strong interlayer coupling between GaSe and MoS . As a result, the photoresponse rate of heterostructures is improved by almost three orders of magnitude compared with that of pristine MoS .