Engineering of point defects semiconductors is important for a variety of applications, including ion implantation/ annealing technology and crystal growth. We have developed two new new approaches to controlling point defect behavior - via the surface and photoexcitation. For example, the degree of chemical bond saturation at surfaces can affect dopant activation and transient enhanced diffusion (TED) in silicon during annealing for ultrashallow junction formation. Point defect such as interstitial atoms can add more easily to unsaturated dangling bonds than to saturated ones. Thus, maintaining an atomically clean surface during annealing greatly increases the annihilation probability. Simulations for boron and experiments for arsenic show that this effect leads to large and simultaneous improvements in dopant activation and TED. We also show that for diffusion rates of arsenic and silicon isotopes are increased nonthermally by more than an order of magnitude for modest illumination intensities of 0.7 W/cm2. Such effects are important in rapid thermal annealing technologies.