We have investigated the effect of rapid thermal annealing (RTA) for the compositional disordering of Si‐implanted AlGaAs/GaAs superlattices (SL) in comparison with that of furnace annealing (FA). By using RTA (970 °C, 10 s), the implantation damage can be eliminated without disordering the SL, while the disordering occurs when FA (850 °C, 30 min) is used. Secondary ion mass spectrometry analyses show that the difference between RTA and FA is due to the extent of Si diffusion into the AlGaAs/GaAs SL.