Effects of Electric Field on the Electronic Structures of Broken-gap Phosphorene/SnX2 (X = S, Se) van der Waals Heterojunctions

Van der Waals heterojunctions (vdWHs) have gained extensive attention because they can integrate the excellent characteristics of the stacked materials and most vdWHs exhibit type-II band alignment. However, type-III vdWHs with broken gaps are still very rare, which limits the development and application of two-dimensional (2D) materials in the fields of tunnel FETs (TFETs). Here, we theoretically demonstrate that 2D phosphorene/SnS2 (SnSe2) vdWHs possess type-III (broken-gap) band alignment, and their I-V curves present negative differential resistance (NDR) effects. The BTBT transport mechanism and its applications in TFETs are analyzed. Interestingly, a positive electric field can enlarge the tunnelling window and a negative electric field can realize multiple-band-alignment transformation (type I, type II, and type III). Thus, this work presents the intrinsic physics mechanism and electric field tunable multiple-band alignments in 2D type-III vdWHs and related electronic devices.