Van der Waals heterostructures of AlAs and InSe: Stacking-dependent Raman spectra and electric field dependence of electronic properties

Abstract

In the present work, the electronic and vibrational properties of a van der Waals type heterostructure, composed of single layers of AlAs and InSe, are investigated using density functional theory (DFT)-based first-principles calculations. Vibrational analyses reveal that dynamically stable single layers of AlAs and InSe form van der Waals type heterostructure which is shown to exhibit stacking-dependent Raman spectra by means of the frequency shifts. According to our findings, a type-II band alignment with a direct band gap of 1.84 eV is found in the ground state stacking of AlAs/InSe vertical heterostructure, in contrast to the indirect band gap behaviors of each individual layer. Moreover, the application of an external vertical electric field shows that the both band alignment type and the electronic behavior of the heterostructure can be tuned. The heterostructure is found to exhibit direct to indirect band gap transition under negative electric field as well as a transition from type-II to type-I heterojunction under negative fields up to 0.3 V/Å. The stronger fields along the same direction results in overlapping of valence states of each layer and lead to a non-linear change of the energy band gap. Overall, the predicted van der Waals type heterobilayer of InSe and AlAs with stacking-dependent vibrational features and well-controlled electronic properties under external field is shown to be potential candidate for optical and optoelectronic applications.