As 1 τ τ ∝ ∝ ⟨ v ⟩ Σ Σ , where Σ Σ is the scattering cross section for electrons and holes at a scattering center and ⟨ v ⟩ is a thermal average (Boltzmann statistics) over all electron or hole velocities in the lower conduction band or upper valence band, temperature dependence of the mobility can be determined. In here, the following definition for the scattering cross section is used: number of particles scattered into solid angle dΩ per unit time divided by number of particles per area per time (incident intensity), which comes from classical mechanics. As Boltzmann statistics are valid for semiconductors ⟨ v ⟩ ∼ ∼ T .