Electrostatic Gating-Dependent Multiple Band Alignments in Ferroelectric α-InSe/α-Te van der Waals Heterostructures.

The two-dimensional ferroelectric van der Waals (vdW) heterojunction has been recognized as one of the most promising combinations for emerging ferroelectric memory materials due to its noncovalent bonding and flexible stacking of various materials. In this work, the first-principles calculations were performed to study the stable geometry and electronic structure of α-InSe/α-Te, incorporating the vdW correction via the DFT-D2 method. The reversal of the polarization direction in α-InSe can induce a transition in the heterostructure from metallic to semiconductor, accompanied by a shift from type-III to type-I band alignment. These changes are attributed to variations in interfacial charge transfer. Analysis of the modulation effects of external electric fields reveals that the P↑ α-InSe/α-Te configuration maintains metallic, whereas the P↓ α-InSe/α-Te configuration exhibits a linear reduction in band gap. Furthermore, both heterostructural configurations will undergo transitions to type-II band alignment transitions at 0.2 V Å and within a range from 0.2 to 0.3 V Å under external electric fields. Our findings offer valuable insights for applications such as ferroelectric memory and static gate devices with multiband alignment.