Hall‐effect measurements are presented for oxidized and unoxidizedp‐type silicon‐on‐sapphire films in the temperature range 77° to 300°K. These measurements show that the dominant scattering mechanism in this temperature range is phonon scattering. The measurements on oxidized films have demonstrated that the mechanism responsible for the observed reduction in acceptor concentration with oxidation is diffusion and preferential redistribution of aluminum from the silicon into the silicon dioxide layer. An additional effect of the oxidation, mobility degradation, is identified as the introduction of scattering centers by the precipitation of neutral aluminum‐oxygen complexes.