Group velocity matters for accurate prediction of phonon-limited carrier mobility

First-principles approaches have recently been developed to replace the phenomenological modeling approaches with adjustable parameters for calculating carrier mobilities in semiconductors.However,in addition to the high computational cost,it is still a challenge to obtain accurate mobility for carriers with a complex band structure,e.g.,hole mobility in common semiconductors.Here,we present a computationally efficient approach using isotropic and parabolic bands to approximate the anisotropy valence bands for evaluating group velocities in the first-principles calculations.This treatment greatly reduces the computational cost in two ways:relieves the requirement of an extremely denseκmesh to obtain a smooth change in group velocity,and reduces the 5-dimensional integral to 3-dimensional integral.Taking Si and SiC as two examples,we find that this simplified approach reproduces the full first-principles calculation for mobility.If we use experimental effective masses to evaluate the group velocity,we can obtain hole mobility in excellent agreement with experimental data over a wide temperature range.These findings shed light on how to improve the first-principles calculations towards predictive carrier mobility in high accuracy.