Diffusion across a Semiconductor-Vapour Interface

General boundary conditions associated with diffusion across a solid - vapour interface are considered in detail and the diffusion equation is solved subject to these boundary conditions. Analytic solutions are derived for: ( a ) diffusion outwards of an impurity into a finite volume with or without simultaneous pumping; ( b ) diffusion inwards from a limited source of impurity, initially in the vapour phase, in a closed system. These results are discussed with reference to the diffusion of Group III and V elements across germanium and silicon surfaces.