Numerical solutions of the time-dependent diffusion equation for positrons implanted near to the surface of a solid, and their application to defect studies, were studied. It was found that, for positrons which were implanted relatively deeply (more than 300nm) within the solid, a single group diffusion model could be used. Results were presented for molecular beam epitaxially grown Si and InP layers. In each case, the trapping rate, defect and bulk lifetimes, diffusion coefficient and surface absorption coefficient could be unambiguously determined.

D.T.Britton, J.Störmer: Applied Surface Science, 1995, 85, 1-7