- The effects of strain‐induced structural defects in a nipi‐doped In0.2Ga0.8As/GaAs multiple‐quantum well sample were studied with time‐resolved electron‐beam‐induced absorption modulation, in which carrier recombination lifetimes and ambipolar diffusion constants are measured with high spatial, spectral, and temporal resolution. Based on a phenomenological model, carrier lifetimes in the limit of weak excitation at room temperature were determined. The lifetime is found to be reduced by a factor of ∼1013 compared to a theoretically calculated value, owing to the presence of strain‐induced defects and alternate recombination channels. By using a two‐dimensional diffusion model, the ambipolar diffusion coefficients Da along high‐symmetry , , and  directions were determined and resulted in an anisotropic behavior such that Da≳Da ≳Da. The anisotropy in diffusion is attributed to corresponding asymmetries in the misfit dislocation density.