Application of time-dependent diffusion models to the study of real solids

The numerical solution of the time-dependent diffusion equation, for positrons implanted near the surface of a solid, and its application to defect studies is presented. For positrons implanted relatively deep inside the solid (≥ 300 nm) a single group diffusion model can be applied. Results are presented for MBE-grown silicon and InP layers. In each case the trapping rate, defect and bulk lifetimes, diffusion coefficient and surface absorption coefficient can be determined unambiguously.