Diffusion of impurities during epitaxy

The diffusion of impurities in both epitaxial layers and the substrate is considered. The differential equations and boundary conditions which describe the problems are derived and solutions are presented for both the idealizations of a semi-infinite substrate and the true thickness of the substrate. Several types of boundary conditions are considered. For the cases of diffusion of impurities with the substrate considered as semi-infinite, the results from digital computation are given in tabular and graphical form. The method of application of the information to the design and production of epitaxial structures is indicated. A comparison is made between the solutions accounting for diffusion during epitaxy and solutions for a rationalized situation in which diffusion is computed by simpler means, and the simpler method is shown to be unsatisfactory for epitaxial calculations.