Stacking order and vertical strain controllable optoelectronic properties of van der Waals heterostructures constructed with germanene and double layer hexagonal structure AlAs

In this study, we use first-principles calculations to investigate the structural and optoelectronic properties of DLHS-AlAs/germanene van der Waals heterostructures (vdWHs) with different stacking orders and vertical strain. The AIMD calculations and binding energies demonstrate that all three DLHS-AlAs/germanene vdWHs are thermally and energetically stable. The interesting transitions from semiconductor to metal and type-I to type-II band alignment can be observed in AB stacking vdWH under vertical strain regulation. Meanwhile, the Dirac cone is always well preserved in all vdWHs. The calculated optical absorption spectra indicate that all vdWHs show enhanced light absorption across the ultraviolet to visible light range, compared to their individual components. Besides, the application of vertical strain can result in the weakening or enhancement of ultraviolet light absorption coefficients in different regions of all vdWHs. Of particular interest is the observation that optical adsorption in the visible light region for all vdWHs is almost always enhanced and broadened with increasing vertical compression strain. These excellent and tunable optoelectronic properties suggest that DLHS-AlAs/germanene vdWHs may have favourable potential for use in optoelectronic devices.