Periodic Reporting for period 1 - EPIC2D (Engineering Electron-Phonon Interactions of Two-Dimensional Materials from First-Principles)
Berichtszeitraum: 2017-07-01 bis 2019-06-30
Specifically, a primary focus of this project is first-principles investigations of the carrier mobilities in 2D semiconductors. Carrier mobility quantifies how fast electrons can travel inside a material and directly affects the switching frequency and power efficiency of electronic devices. Therefore, carrier mobility is a critical design parameter for electronics and optoelectronics. In a clean semiconductor crystal, the carrier mobility near room temperature is limited by the EPIs in the solid. Recent methodology developments in the host’s group enable the prediction of the carrier mobility of semiconductors using a Boltzmann transport equation approach that treats the EPIs from first principles. In this project, we employ these newly developed methods to study the EPIs and carrier mobilities of 2D semiconductors.
We have further investigated the effect of EPIs on the electron effective mass of InSe. For semiconductors, the carrier effective mass is a key parameter that affects a wide range of properties, including the carrier mobility. Many-body interactions, including both the electron-electron interactions (EEIs) and EPIs, can renormalize the carrier effective mass and lead to mass enhancement. The nature and strength of many-body interactions in InSe were not clear before. We employ many-body perturbation calculations to investigate the EEIs and EPIs in bulk InSe, as well as their influence on the renormalization of the electron effective mass. Surprisingly, we find that EEIs lead to a significant directional anisotropy in the mass enhancement, which we explain in terms of the symmetry of band-edge wavefunctions. Furthermore, we find that the main contribution to the EPI-induced mass enhancement originates from the Fröhlich interaction. The weak Fröhlich interaction in InSe leads to a weak polaronic mass enhancement, which is desirable for device applications. Our results provide important insight into the nature and strength of many-body interactions in InSe. The comprehensive study of the many-body renormalization of electron effective mass will be useful for designing electronics and optoelectronics based on InSe and other similar layered semiconductors such as GaS and GaSe. The work leading up to these results has been submitted for publication.