Strain- and Electric Field-Induced Band Alignment Transitions in a GaSe/ZrSe2 van der Waals Heterostructure

Abstract

Abstract Two-dimensional (2D) van der Waals heterostructures (vdWHs) have emerged as a highly versatile platform for designing next-generation optoelectronic devices. In this study, we perform systematic first-principles calculations to investigate the structural, electronic, and optical properties of the GaSe/ZrSe2 vdWH, as well as its responses under biaxial strain and perpendicular external electric fields. Our results predict that the equilibrium vdWH exhibits an indirect bandgap of 1.18 eV with a prominent Type-I band alignment, which effectively confines both photoexcited electrons and holes within the ZrSe2 layer. Furthermore, we demonstrate that a transition from Type-I to Type-II band alignment can be dynamically induced either by applying a tensile strain of +2% or higher, or a positive external electric field exceeding +0.2 V/Å, thereby facilitating the spatial separation of photogenerated carriers. Concurrently, the optical spectral profiles can be strategically manipulated because biaxial strain prominently boosts visible-light absorption while modulating the omnidirectional reflectance and transmittance, whereas external electric fields enable precise regulation over the infrared and ultraviolet responses. These fundamental insights into the underlying microscopic mechanisms position the GaSe/ZrSe2 vdWH as a promising dynamically controllable building block for multifunctional nanodevices such as strain gauges, ultraviolet photodetectors, transparent optoelectronics, and highly efficient photocatalytic systems.