Uncovering the important role of transverse acoustic phonons in the carrier-phonon scattering in silicon

Carrier mobility is an essential parameter of semiconductors, characterizing how quickly carriers can move in a material when driven by an external electric field. Because electron-phonon (e-ph) scattering limits the room-temperature carrier mobility in high-quality semiconductors, understanding the mechanisms of interaction between carriers and phonons at the microscopic level is vital to investigate the transport properties, especially in nanoelectronic devices. Here, we reproduce the experimentally measured electron and hole mobility in silicon (Si) over a wide temperature range without relying on adjustable parameters by performing the first-principles calculations. By decomposition of the first-principles calculation-predicted e-ph scattering into the contributions from different phonon modes and electronic valleys, we show that the transverse acoustic (TA) phonon mode has a comparable contribution to the longitudinal acoustic (LA) phonon mode in scattering of both electrons and holes on limiting the carrier mobilities in Si. This is in striking contrast with the common sense that the TA mode is negligible based on the classical e-ph interaction modes. We unravel that the neglect of TA scattering is due to the substantial underestimation of the shear deformation potential (associated with the TA mode) with respect to the dilation deformation potential (associated with the LA mode). We also find that the transverse optical (TO) phonon mode, rather than the conventionally presumed longitudinal optical (LO) and LA modes, provides the leading scattering channel (accounting for 58%) in $f$-type intervalley scattering and the LO mode is dominant over the LA mode in $g$-type intervalley scattering for electrons in Si. These findings illustrate why the technology computer-aided design device simulation loses the predictive capability, although it is possible to obtain reasonable results using adjustable parameters based on the incorrect physics models. It calls for a revisit of the mechanisms underlying the carrier mobility in semiconductors.