Tunable Electric Properties of Bilayer α-GeTe with Different Interlayer Distances and External Electric Fields

Abstract

Based on first-principle calculations, the stability, electronic structure, optical absorption, and modulated electronic properties by different interlayer distances or by external electric fields of bilayer α-GeTe are systemically investigated. Results show that van der Waals (vdW) bilayer α-GeTe has an indirect band structure with the gap value of 0.610 eV, and α-GeTe has attractively efficient light harvesting. Interestingly, along with the decrease of interlayer distances, the band gap of bilayer α-GeTe decreases linearly, due to the enhancement of interlayer vdW interaction. In addition, band gap transition is originated from the electric field-induced near free-electron gas (NFEG) under the application of positive electrical fields. However, when the negative electric fields are applied, there is no NFEG. On account of these characteristics of bilayer α-GeTe, a possible data storage device has been designed. These results indicate that bilayer α-GeTe has a potential to work in new electronic and optoelectronic devices.

Electronic, Optical, and Thermoelectric Properties of Bulk and Monolayer Germanium Tellurides

“…Accordingly, we carefully consider the puckered monolayer GeTe as an indirector a quasidirect-gap semiconductor with gap of 0.90 eV, in good agreement with a previous study by the optPBE-vdW method, which is a kind of GGA variation [19]. Our calculations also suggest that buckled monolayer GeTe is an indirect-gap semiconductor with band gap of about 1.81 eV, which is consistent with prior studies when they do not include the HSE correction [20,24,33,34]. The indirect gap for the buckled GeTe is due to the valence band maximum at the Γ point and the conduction band minimum along the Γ-M path.…”

“…The lattice constants (a, b, c) and angles (α, β, γ) are in accordance to the illustrations in Figure 1. a = b = 3.961 3.950 [33], 3.955 [34], 3.960 [20,24] To achieve the convergence in the DFT simulation while considering a reasonable calculation time, we set the kinetic energy cutoff for the wave function in this work to 50 Ry and the convergence threshold for successive iteration as low as 10 −9 Ry. The electronic wave vectors k in the Brillouin zone are sampled using the Monkhorst-Pack scheme [35] with quite dense 32 × 32 × 32 and 48 × 48 × 1 k-point grids for the bulk and monolayer GeTe, respectively.…”

Low-cost pentagonal NiX2 (X = S, Se, and Te) monolayers with strong anisotropy as potential thermoelectric materials

“…A vacuum distance of 20 Å is adopted to avoid the interactions between the pentagonal NiX 2 (X = S, Se, and Te) monolayers and their periodic structures. 47 The empirical Grimme's correction is employed to evaluate the van der Waals (vdW) interactions. 48 The Heyd–Scuseria–Ernzerhof (HSE06) hybrid functional 49 is utilized to obtain the accurate electronic structure and band gap.…”

Infrared photovoltaic detector based on p-GeTe/n-Si heterojunction

“…GeTe material has attracted extensive attention in recent years [11][12][13][14][15]. It has been considered as a strong contender for the next-generation memory technology as the material exhibits different physical, electrical, and optical properties when it is in amorphous and crystal phases [16][17][18][19][20][21].…”