Structure–Property Relationship of Low-Dimensional Layered GaSe_xTe_1–x Alloys

Abstract

We report the growth of layered GaSe x Te 1−x mesostructures across the whole composition range. For compositions up to x = 0.32 (the Te-rich region), mesocrystals form predominantly in the monoclinic structure, similar to naturally occurring GaTe. However, the hexagonal crystal structure, similar to naturally occurring GaSe, begins growing at the x = 0.28 composition and grows almost exclusively in the range of x = 0.32 to pure GaSe, establishing a region of composition where both monoclinic and hexagonal crystals exist. While the optical bandgap of the monoclinic phase increases linearly from 1.65 to 1.77 eV with increasing Se content, the incorporation of Te in the hexagonal phase reduces the optical gap from 2.01 (pure GaSe) to 1.38 eV (x = 0.28). Specifically, a bandgap difference of ∼0.35 eV between monoclinic and hexagonal crystals is observed in the composition range where both crystal structures can be grown. These observations are in good agreement with direct-gap trends calculated by density functional theory, which show a linear dependence on composition for the direct gap of the monoclinic phase and a considerable bowing of the direct gap of the hexagonal phase for Te-rich compositions. Our results show that layered semiconductor alloys are remarkably versatile systems in which electronic properties can be controlled by not only thickness but also structural phase and composition.

Recent advances in low‐dimensional semiconductor nanomaterials and their applications in high‐performance photodetectors

“…39 The bandgap can be easily controlled by alloying to find better performance and more suitable materials. 41,[60][61][62][63] The IV-VI compound has the same unique orthogonal lattice structure as B-P ( Figure 4H-J) and strong anisotropic characteristics. 42,69 The adjustable bandgap, high electron mobility, and good optical response, light absorption, and other characteristics make these 2D semiconductors have good application value in the field of optoelectronics.…”

“…Figure D shows a typical lattice structure of InSe which is representative of the III‐VI compound . The bandgap can be easily controlled by alloying to find better performance and more suitable materials …”

“…Bandgap distribution map and lattice structure diagram of different 2D semiconductor materials and alloys. Reproduced with permission (list only some typical values of materials). Copyright 2015, Wiley‐VCH; Copyright 2019, Elsevier B.V; Copyright 2017, Elsevier B.V; Copyright 2015, American Chemical Society; Copyright 2018, Wiley‐VCH; Copyright 2018, American Chemical Society; Copyright 2017, Elsevier B.V; Copyright 2018, Wiley‐VCH; Copyright 2014, IOP Publishing, Ltd; Copyright 2011, ROYAL SOCIETY OF CHEMISTRY; Copyright 2016, American Chemical Society…”

“…The lattice similarity of different TMDs F I G U R E 1 Bandgap distribution map and lattice structure diagram of different 2D semiconductor materials and alloys. Reproduced with permission 18,21,23,34,38,41,48,58,61,74,75 23 a large area of HfS 2(1 − x) Se 2x alloy can be directly grown by chemical vapor deposition (CVD), and its composition can be continuously adjusted. As the Se content increases, the bandgap of the alloy can vary continuously from 2.64 to 1.94 eV ( Figure 2D,G).…”

2D Materials Based on Main Group Element Compounds: Phases, Synthesis, Characterization, and Applications

“…Here, the hexagonal phase was prepared when the Se content was above 20% (Figure 3b). [77] Cai et al further indicated the presence of a mixed region, where both the phases could coexist, and two bandgaps for the same composition. [78] Zhao et al observed that the metastable hexagonal phase may resist when the number of layers decreases further to 1-3 because of the surface effect.…”