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Abstract
The interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors. In this work, comprehensive investigations on full electron–phonon (el–ph) couplings and their influences on carrier mobility and thermoelectric (TE) performances of 2D group IV and V elemental monolayers are performed, and we also analyze the selection rules on el–ph couplings using group theory. For shallow n/p-dopings in Si, Ge, and Sn, ZA/TA/LO phonon modes dominate the intervalley scatterings. Similarly strong intervalley scatterings via ZA/TO phonon modes can be identified for CBM electrons in P, As, and Sb, and for VBM holes, ZA/TA phonon modes dominate intervalley scatterings in P while LA phonons dominate intravalley scatterings in As and Sb. By considering full el–ph couplings, the TE performance for these two series of monolayers are predicted, which seriously downgrades the thermoelectric figures of merits compared with those predicted by the constant relaxation time approximation.
Highlights
Among the extraordinary properties in 2D materials, carrier transport properties play the key role in determining the performance in microelectronic, optoelectronic and thermoelectric devices
The deformation potential approximation (DPA) method based on the intravalley coupling between electrons and long-wavelength longitudial acoustic (LA) phonon modes[5,6], was widely used to estimate or understand the carrier mobilities in many non-polar 2D semiconductors including graphene[7], phosphorene[8] and transition metal dichalcogenide (TMD)[9]
In some polar or highly anisotropic systems, the DPA method usually misestimates the intrinsic carrier mobility, in which the coupling from the longitudinal optical (LO) phonon modes described as the Fro€hlich interaction, and the direction-dependent contributions can not be neglected
Summary
Two-dimensional (2D) materials offer challenging opportunities for a wide range of applications in nanoscale devices. Inspired by the extraordinary properties of graphene, the group IV elemental materials of silicene (Si), germanene (Ge), and stanene (Sn) as the promising alternatives, have attracted tremendous interests Studies show that such monolayers all possess Dirac fermions similar to graphene, high mechanical flexibility and high electron mobility, leading to the potential applications in batteries and topological devices[12,13]. Based on the first principles method, we systematically investigate the full el–ph coupling effects in 2D group IV and V materials These two series of 2D materials possess a broad range of carrier mobilities, which may lead to various applications. Arsenene, and antimonene, despite the different bands and locations of valence-band maximum (VBM), LA phonon modes with A irreducible representation (irreps) of C2 group near Γ point dominate the intravalley scatterings due to the identical symmetry and irreps of the intial and final electronic states. By considering the full el–ph scatterings, an accurate prediction of the carrier transport properties and thermoelectric performances of these two series of materials are achieved
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