We present investigations on the interdiffusion behavior and thermal stability ofn‐doped and undoped GaInAs/AlGaInAs multiple‐quantum‐well structures, grown lattice matched on InP by molecular‐beam epitaxy. The activation energy of the main interdiffusion process is determined toEan doped=2.5 eV andEaundoped=2.9 eV. The different interdiffusion processes are monitored mainly by photoluminescence spectroscopy atT=8 K after rapid thermal annealing of the samples. The influence of doping is studied by comparing the results ofn‐doped and undoped structures. Additionally photoluminescence excitation spectroscopy atT=2 K was carried out to verify the different interdiffusion processes. ©1995 American Institute of Physics.