The diffusion of phosphorus from a thick epitaxial layer into a silicon substrate has been investigated using the spreading-resistance technique. By comparing the diffusion profile under a free oxidized surface with the profile under a masked surface, it has been shown that surface oxidation enhances diffusion at low temperatures and retards diffusion at high temperatures. The conditions which favor enhanced diffusion are those under which stacking faults grow; retarded diffusion is associated with stacking-fault shrinkage. Enhanced diffusion is due to the oxide injecting excess interstitials into the substrate; retarded diffusion is caused by vacancy injection. It is concluded that phosphorus diffuses by the interstitialcy mechanism and that the criterion for interstitial or vacancy injection is the relative value of the anion and cation fluxes across the oxide-silicon interface.

The origin of the dislocation climb which takes place in the presence of electron-hole recombination in laser structuresis discussed. TEM studies on lasers which have been degraded by either forward bias or by optical pumping show that the climb dipoles are extrinsic in both cases. In addition, completely isolated interstitial loops can form which also have the characteristic climb appearance of the larger dipoles. Existing theories for the origin of the interstitials required to account for the observed climb are considered in detail, and it is concluded that the climb structures can best be explained by the emission of both gallium and arsenic vacancies from the dislocation as a consequence of nonradiative processes occurring at the dislocation core.

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