General rules and applications for screening high phonon-limited mobility in two-dimensional semiconductors

Two-dimensional (2D) semiconductors with high mobility comparable to three-dimensional (3D) Si or GaAs are still lacking, hindering the development of high-performance 2D devices. In this work, based on the phonon-energy resolved matching function between the electronic band structure and the phonon spectrum recently proposed in our group, we provide some general rules for screening possible high-mobility 2D semiconductors. In general, a 2D semiconductor with high sound velocity, small effective mass, large atomic mass, high-energy optical phonons, small Born effective charge, large effective in-plane dielectric constant, and large effective layer thickness, is likely to have high phonon-limited mobility. Additionally, if the semiconductor has multiple valleys, the mobility-limiting factor due to intervalley scattering can be weak if the valleys are far apart in reciprocal space and have out-of-plane orbitals. Guided by these rules, we have systematically explored the mobility of traditional semiconductors at the 2D limit (2DTSs), which have been theoretically predicted and experimentally realized recently. Seven 2DTSs are found to have mobilities close to or exceeding 1000 $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Most notably, BSb reaches record-high values of several thousand $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$ at room temperature and the experimentally synthesized 2D AlSb has an electron mobility of 921.9 $\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.16em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1}$. Using BSb, InN, and AlSb as examples, we reveal that, although the high mobilities of these systems are attributed to different underlying scattering mechanisms, they can all be understood from our proposed general rules. The present work demonstrates that 2DTSs can achieve comparable carrier mobility to 3D, thus opening possible doors to 2D high-performance electronic devices.