The surface layer of single crystal GaAs that has been bombarded with high energy (2-15 MeV) ions is strained and contains many defects, but it remains crystalline. We have studied the isochronal annealing behavior of this layer using phonon shifts and widths, which were detected by Raman measurements. We do not find any sharp annealing stages to 500 C, at which temperature the phonons have returned to their positions in the unbombarded crystals. These results are consistent with the idea that the phonon shifts are primarily due to antisites and their complexes with other primary defects. However, other extended defects may still be present, and the Raman data show some evidence for this.