Raman scattering has been used to track structural information on arsenic clusters in GaAs obtained by annealing of high dose As‐implanted GaAs layers. Beyond the good crystalline quality of both the clusters and the matrix, high tensile stresses within the precipitates have been originally deduced from the A 1g and E g mode frequency shifts. The results are well explained in terms of the difference between the thermal expansion coefficients of the two materials. The temperature dependence of the stresses corroborates this interpretation. © 1995 American Institute of Physics.