Electric field and strain induced gap modifications in multilayered GaN

Abstract

Two-dimensional materials with a wide bandgap characteristic are critical to developing novel nanoscaled electronic devices. This study investigates the layer, in-plane biaxial strain, and vertical external electric field effects on the stability and electronic properties of multilayered GaN employing the density functional theory. Using structural optimization and phonon-mode calculations, the GaN structures with one to five layers are found to be stable and refer to the Born–Oppenheimer local minima. Under dimensionality effect, GaN unveils a semiconducting feature with an indirect bandgap at the HSE06 level that changes from 3.37eV for a monolayer to 2.79eV for a five-layered structure as the quantum confinement effect is reduced. The calculations demonstrate that the indirect bandgap of multilayered GaN decreases linearly when increasing the tensile strain. However, compressive strain engineering would induce an indirect-to-direct gap transition. Additionally, when the strength of the applied perpendicular external electric field to the multilayered GaN surface is increased, the GaN bandgap rapidly disappears due to the field-induced near free electronic gas. Calculated carrier effective mass indicate that both external effects impact charge carrier mobility as well. Such significant changes in the electronic properties under external excitations show that multilayered GaN shows promise in configurable nanoelectronic devices.