The effect of subsequent annealing treatment on electrical properties of aluminum‐implanted silicon was studied by means of Hall‐effect and sheet‐resistivity measurements. Implanted silicon samples were annealed under various schedules, for example, isochronal annealing for 20 min, isothermal annealing at 800°C, etc. A sign conversion of ``sheet Hall coefficient (RHS)'' in the implanted layer of ``over annealed'' sample was observed below room temperature. However, hot probe measurements on the same sample showed the existence of p‐type layer, and the photo voltaic effect was also observed indicating that p‐n junction existed.
We have tentatively attempted to explain that these anomalous electrical properties were due to precipitation of implanted aluminum atoms along crystal imperfections.