Forward current-voltage characteristics and reverse recovery of high-voltage p–i–n diodes based on Al_xGa_1–xAs_1–ySb_y layers with x ranging from 0 to 0.6 and y ranging from 0 to 0.2, manufactured by liquid-phase epitaxy due to self-doping with background impurities, have been studied. The forward current-voltage characteristics, described as a sum of the recombination current in the space charge region and the diffusion current in the base, have been  observed at low current densities for p⁰–i–n⁰ junctions of GaAs, Al_xGa_1–xAs and Al_xGa_1–xAs_1–ySb_y with x up to 0.6 and y up to 0.04. The effective lifetime of nonequilibrium charge carriers decreases from ~ 170 ns in GaAs layers to  30–60 ns in the layers of Al_xGa_1–xAs with x ranging from 0.2 to 0.45 and to 4–12 ns in Al_xGa_1–xAs_1–ySb_y layers.