We show that the degree of irreversible structural damage of samples implanted to 1019 cm(-3) is much less than that measured in samples implanted to 10(20) cm(-3). The RBS/channeling chi(min) is 4.95 for the samples annealed at 1400, 1500, and 1600degreesC and drops to 2.0 for the 1700degreesC anneal. TEM shows that small extended defects are present in. There are fewer of them at the higher annealing temperatures, although they are larger, and they are concentrated closer to the surface. HREM shows the extended defects are structural and appear to be stacking faults or dislocations.