Detailed impact ionization (II) analysis of electrons is presented for AlGaN alloys as a vital resource for solar-blind avalanche photodiode and high power transistor applications. Necessary ingredients for the II characterization are supplied from a recent experiment on the GaN end, and a Keldysh analysis for the AlN end, of the alloy AlGaN. High-field electron dynamics are simulated using an ensemble Monte Carlo framework, accounting for all valleys in the lowest two conduction bands, obtained from accurate empirical pseudopotential band structure computations. The effect of alloy scattering on II is considered and observed to be significant. For any AlxGa1-xN alloy, the electron II coefficients are found to obey the form, A exp(-K/F), for the electric field, F.