Role of flexural phonons in carrier mobility of two-dimensional semiconductors: free standing vs on substrate

Abstract

Two-dimensional (2D) semiconductor is a promising material for future electronics. It is believed that the flexural phonon (FP) induced scattering plays an important role in the room-temperature carrier mobility, and the substrate can significantly affect such scattering. Here we develop an ‘implicit’ substrate model, which allows us to effectively quantify different effects of the substrate on the FP scattering. In conjunction with the first-principles calculations, we study the intrinsic mobilities of the holes in Sb and electrons in MoS2 as representative examples for 2D semiconductors. We find that the FP scattering is not dominant and is weaker than other scatterings such as that induced by longitudinal acoustic (LA) phonon. This is due to the significantly smaller electron–phonon-coupling (EPC) matrix elements for the FP compared with that for the LA phonon in the free-standing case; although the substrate enhances the FP EPC, it suppresses the FP population, making the FP scattering still weaker than the LA scattering. Our work improves the fundamental understanding of the role of FP and its interaction with the substrate in carrier mobility, and provides a computational model to study the substrate effects.