The surface blisters in B+/H+ coimplanted germanium (Ge) and H-only-implanted Ge were compared. The surface-blister phenomenon in B+/H+ coimplanted Ge emerged after annealing at 330-340 degrees C; but in H-only-implanted Ge, the blistering emerged after annealing at over 400 degrees C. The results indicate that the preimplanted boron can facilitate the coalescence of implanted H into bubbles, and so, it decreases the temperature for surface-blister formation. The exfoliation mechanism of B+/H+ coimplanted Ge during the annealing step was investigated. The transmission electron microscopy results indicate that the B+/H+ coimplantation creates both (100) and {111} platelet defects, and the nucleation of H bubbles occurs at regions where the (100) defects are concentrated. The bottoms of popped-off blisters show a very rough surface because the (100) and {111} platelets occur at different depths, and the wide distribution of (100) platelets also contributes to this roughness. The results show that boron appears to be one of the choices for prebonding implantation because it reduces the splitting temperature of the H-implanted Ge wafer.