The temperature dependencies of these two scattering mechanism in semiconductors can be determined by combining formulas for τ, Σ and ⟨ v ⟩ , to be for scattering from acoustic phonons μ μ p h ∼ ∼ T − − 3 / 2 and from charged defects μ μ def ∼ ∼ T 3 / 2 .