Orientation-Dependent Transport and Photo detection in WSe2/MoSe2 Planar Heterojunction Transistors

The tight contact interface of the planar heterojunction provides great opportunities for electronic and optoelectronic devices. However, the relationship between device performance and orientation has not been systematically investigated. Here, by using the density functional theory combined with nonequilibrium Green's function method, we simulate the field-effect transistors (FETs) based on p-n WSe 2 /MoSe 2 planar heterojunction, where electrical transport and photodetection characteristics are strongly dependent on the orientation. The rectification ratio R-r can reach up to 10( 11) along the armchair direction, and enhance five orders of magnitude under gate voltage modulation. In addition, it can achieve broadband photodetection in the zigzag direction, while it is more sensitive to ultraviolet light in the armchair direction. Especially, the photocurrent density, photoresponsivity, and external quantum effect of the device along the zigzag direction with a gate voltage of 1 V reach 47 nA/m, 160 mA/W, and 46%, respectively, which is twice as high as that in the armchair direction. This work provides a route to realize orientation-dependent multifunctional nanodevices.