h-AlN-Mg(OH)2 vdW Bilayer Heterostructure: Tuning the excitonic characteristics

Physical Review B 95, 075423 (2017)

h-AlN-Mg(OH)2 vdW Bilayer Heterostructure: Tuning the excitonic characteristics

C. Bacaksiz,A. Dominguez,A. Rubio,R. T. Senger,, H. Sahin

Motivated by recent studies that reported the successful synthesis of monolayer Mg(OH)2 [Suslu et al., Sci. Rep. 6, 20525 (2016)] and hexagonal (h-)AlN [Tsipas et al., Appl. Phys. Lett. 103,251605 (2013)], we investigate structural, electronic, and optical properties of vertically stacked h-AlN and Mg(OH)2, through ab initio density-functional theory (DFT), many-body quasi-particle calculations within the GW approximation, and the Bethe-Salpeter equation (BSE). It is obtained that the bilayer heterostructure prefers the AB′ stacking having direct band gap at the 􀀀 with Type-II band alignment in which the valance band maximum and conduction band minimum originate from different layer. Regarding the optical properties, the imaginary part of the dielectric function of the individual layers and hetero-bilayer are investigated. The hetero-bilayer possesses excitonic peaks which appear only after the construction of the hetero-bilayer. The lowest three exciton peaks are detailedly analyzed by means of band decomposed charge density and the oscillator strength. Furthermore, the wave function calculation shows that the first peak of the hetero-bilayer originates from spatially indirect exciton where the electron and hole localized at h-AlN and Mg(OH)2, respectively, which is important for the light harvesting applications.

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The calculations were performed at TUBITAK ULAKBIM, High Performance and Grid Computing Center (TR-Grid e-Infrastructure). CB and RTS acknowledge the support from TUBITAK Project No 114F397. HS acknowledges support from Bilim Akademisi-The Sci- ence Academy, Turkey under the BAGEP program. HS acknowledges financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) under the project number 116C073. AR and AD acknowledge financial support from the European Research Council(ERC-2015-AdG-694097), Spanish grant (FIS2013-46159-C3-1-P), Grupos Consolidados (IT578-13), and AFOSR Grant No. FA2386-15-1-0006 AOARD 144088, H2020-NMP-2014 project MOSTOPHOS (GA no. 646259) and COST Action MP1306 (EUSpec).

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