The effects of Zn doping in the substrate on the thermal stability of GaAs/Al0.24Ga0.76 As single quantum well are investigated by 900 degreesC rapid thermal annealing and low-temperature (12 K) photoluminescence measurements. An improvement in thermal stability is demonstrated for structures grown on Zn-doped GaAs in comparison with those grown on semi-insulating and Si-doped GaAs substrates. It is likely that the Zn out-diffusion from the substrate to the quantum well region has lowered the Al-Ga interdiffusion coefficient. (C) 2003 Elsevier Science B.V. All rights reserved.