InP wafers with very low residual Fe concentrations were subjected to a two-step wafer annealing procedure and were then measured by photoluminescence. A sharp line at 1.3618 eV was clearly observed after the first step high temperature annealing, and was largely reduced after the second step medium temperature annealing. This sharp line seems to be due to vacancy-related defects. The reduction may cause the improvement of the electrical property uniformity.