. µ i is the mobility resulting from ionised impurity scattering (here, the native acceptors). This term is expected to be nearly temperature-independent for a degenerate semiconductor. µ p (T ) ≡ AT γ is a temperature-dependent mobility resulting from phonon scattering. Fitting µ i , A and γ to the experimental mobility (shown in green) yields µ i = 45.2 cm 2 V -1 s -1 and γ = -2.06 (Figure ). According to theory developed for ptype III-V semiconductors, γ = -1.5 for purely acoustic phonon scattering and γ < -1.5 when contributions from optical phonons are also present. Similar to CaCuP, III-V semiconductors have a doubly degenerate valence band maximum at the Γ point and typically γ ≃ -2.3. 57,58