Effects of electron-phonon intervalley scattering and band non-parabolicity on electron transport properties of high-temperature phase SnSe: An ab initio study

Abstract

High-temperature phase tin selenide (β-SnSe) possesses a large power factor owing to its innately complex band structure. A detailed analysis of the electron-phonon (e-ph) intervalley scattering between the different non-parabolic valleys in β-SnSe remains to be disclosed. Using ab initio approach, the phonon-limited carrier mobility, Seebeck coefficient, and power factor in the range from 800 to 950 K were calculated. The e-ph intervalley scattering was shown to drastically increase the electron scattering rates, particularly in the processes involving acoustic or transverse-optical phonons. This scattering suppresses the mean free path of holes and electrons to less than 2 nm, which is detrimental to the power factor. As the temperature increases, the hole and electron mobilities decrease with the relations from T−2.38 to T−3.47 in different crystallographic directions, the values which drop much faster than the predictions given by the typical T−1.5 dependence, partly because of the high non-parabolicity of the band structure. This study highlights the necessity of explicitly considering the synergetic effect from the e-ph intervalley scattering and band non-parabolicity when modeling the electron transport of β-SnSe.