- High electric field transport in n‐Ga1− x Al x As semiconductor alloys for composition x range from 0.0 to 0.5 is studied theoretically. The calculations are based on a shifted Maxwellian approach for the three‐valley conduction‐band model. An expression for the alloy scattering probability involving no fitting parameters is used in these calculations. The calculations predict a close to linear decrease of peak velocity with an increase in the alloy composition x. The absence of the onset of negative differential mobility at x≥ 0.35 is found.