Ab-initio study of strain-tunable g-GaN/BN nanoheterostructure for optoelectronic and photocatalytic applications

Two-dimensional (2D) nanoheterostructures of materials, integrating various phase or materials into a single nanosheet have stimulated large-scale research interest for designing novel two dimensional devices. In contemporary analysis present work, we examined the structural and electronic properties of the isolated 2D BN and GaN monolayers. We have investigated the structural stability and optoelectronic and photocatalytic response of the g-GaN/BN nanoheterostructure along with its response to strain. Nanoheterostructure g-GaN/BN is predicted to be a direct bandgap semiconductor with wide gap of 4.45 eV, whose value can be effectively modulated by applied strain ( $ϵ)$ , ranging from 4.55 ( $ϵ$ = - 4%) to 3.58 eV ( $ϵ$ = 8%). We also discovered that the tensile strain of 8% can substantially tune the direct bandgap of nanoheterostructure to indirect band gap nature. Even more important, the biaxial tensile strain engineering accentuates an enhancement of optical absorption in the UV region, broadening the light harvesting of the g-GaN/BN nanoheterostructure with the shifting of first absorption peak from 4.64 ( $ϵ$ = - 4%) to 3.71 eV ( $ϵ$ = 8%). Furthermore, strain-tuned band edge potentials arrangement perfectly fits the water reduction and oxidation redox potentials. Our findings portend that the g-GaN/BN nanoheterostructure has application in prospective nanoscale optoelectronic devices and photocatalytic hydrogen evolution system.

First principles calculations in this study are performed using density functional theory. Generalized gradient approximation within PBEsol functional employed to address the electron-electron exchange-correlation effects. For avoiding periodic interactions between the layers, we have inserted a vacuum region of thickness 10 Å in the z-direction. For ensuring the convergence accuracy of the computed results, convergence criteria of the iteration process is set to be 0.0001 eV. Local modified Becke-Johnson, a semi local functional, is applied for calculating electronic and optical properties for more accuracy of results. As in layered 2D nanoheterostructure, a factual depiction of the van der Waals interactions cannot be provided by conventional DFT techniques. Accordingly, in order to incorporate these interactions, we had employed the dispersion correction method of Grimme's.