Band alignments tuned by spontaneous polarization in two-dimensional MoS2/GaN van der Waals heterostructures

Abstract

The band alignment of van der Waals (vdW) heterostructures is crucial for evaluating their carrier behavioral characteristics and application prospects. The shift of energy bands on the component surfaces induced by the out-of-plane spontaneous polarization effect provides an alternative method for tuning the band alignments of vdW heterostructures. Herein, we investigated the effect of the spontaneous polarization direction of the two-dimensional (2D) buckled GaN layer on the electronic properties of 2D MoS 2 /GaN heterostructures based on density functional theory (DFT). The calculation results indicated that the varying polarization direction of the GaN layer could significantly shift the band edges of the components, thereby realizing the conversion between the type-I and II band alignments without applying an external electric field. Combining the rational design of spontaneous polarization direction and the regulation of external electric fields, specific band alignment types and bandgaps can be achieved with high efficiency and low energy consumption. Furthermore, the overlap of electronic states and new optical transitions induced by interlayer coupling improved the optical absorption coefficients and absorption ranges of MoS 2 /GaN heterostructures compared with the corresponding monolayers. The results suggest that MoS 2 /GaN heterostructures with tunable band alignments are promising candidates for future optoelectronic device applications. • Tuning the band alignments of vdW heterostructures by utilizing the out-of-plane spontaneous polarization of 2D buckled GaN. • 2D MoS 2 /GaN heterostructure converts between type-I and II band alignments by varying polarization direction of GaN layer. • 2D MoS 2 /GaN heterostructure with improved optical absorption coefficient and absorption range. • Specific bandgaps is realized under the combined action of the polarization electric field and the external electric field.