Abstract
Two-dimensional MX (M = Ga, In; X = S, Se, Te) homo- and heterostructures are of interest in electronics and optoelectronics. Structural, electronic and optical properties of bulk and layered MX and GaX/InX heterostructures have been investigated comprehensively using density functional theory (DFT) calculations. Based on the quantum theory of atoms in molecules, topological analyses of bond degree (BD), bond length (BL) and bond angle (BA) have been detailed for interpreting interatomic interactions, hence the structure–property relationship. The X–X BD correlates linearly with the ratio of local potential and kinetic energy, and decreases as X goes from S to Te. For van der Waals (vdW) homo- and heterostructures of GaX and InX, a cubic relationship between microscopic interatomic interaction and macroscopic electromagnetic behavior has been established firstly relating to weighted absolute BD summation and static dielectric constant. A decisive role of vdW interaction in layer-dependent properties has been identified. The GaX/InX heterostructures have bandgaps in the range 0.23–1.49 eV, absorption coefficients over 10−5 cm−1 and maximum conversion efficiency over 27%. Under strain, discordant BD evolutions are responsible for the exclusively distributed electrons and holes in sublayers of GaX/InX. Meanwhile, the interlayer BA adjustment with lattice mismatch explains the constraint-free lattice of the vdW heterostructure.
Highlights
Two-dimensional (2D) materials with van der Waals interlayer interactions are predicted to expand the emerging thin-film family in electronics and optoelectronics fields due to their unique planar and layer-dependent properties [1,2,3,4,5]
Demirci et al [19] found that III–VI monolayers are thermally stable with adequate stiffnesses and rigidities and of wide-spreading bandgaps
Chen et al [17] found that the intrinsic mobility in III–VI monolayer is limited by the phonon scattering mode
Summary
Two-dimensional (2D) materials with van der Waals (vdW) interlayer interactions are predicted to expand the emerging thin-film family in electronics and optoelectronics fields due to their unique planar and layer-dependent properties [1,2,3,4,5]. Layer-dependent electronic and dielectric properties of Ga chalcogenides and mechanically tunable bandgaps in monolayers make them ideal candidates for nanoelectronics and optics [24]. Competitive 2D vdW heterostructures should have diverse electronic performances, favorable band alignments and high PV effects as results of mutual efforts of sublayers [27]. Jappor et al [30] found that the GaS/GaSe heterostructure has a direct bandgap with the value smaller than that of the constitutive monolayers. Our research is of great bearing in understanding the structure–property relationship of III-VI materials, shedding light on discovering promising 2D vdW materials
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