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Studies of the Push‐Out Effect in Silicon: II . The Effect of Phosphorus Emitter Diffusion on Gallium‐Base Profiles, Determined by Radiotracer Techniques

1976; Institute of Physics; Volume: 123; Issue: 10 Linguagem: Inglês

10.1149/1.2132632

1945-7111

C. L. Jones, A. F. W. Willoughby,

Silicon Nanostructures and Photoluminescence

The push‐out of gallium‐diffused base layers underneath subsequently diffused phosphorus emitters, has been studied using 67Ga to obtain the complete tracer profiles of the base both within and beyond the emitter. The profiles show two major features which can be treated separately. Firstly, the depression of the base‐collector junction in push‐out is found to be due entirely to movement of Ga atoms, representing a very large enhancement of diffusion beyond the emitter. For the emitter diffusions used in this work, the magnitude of this enhancement varies from ∼8 for a 1050°C emitter diffusion to ∼100 for a 900°C emitter diffusion. The mechanism of diffusion enhancement in push‐out is discussed in the light of the new data, and is considered to be due to production of an excess of a mobile point defect by high concentration phosphorus diffusion. The nature of the point defect, and the generation mechanism are, however, still to be resolved. Secondly, the tracer profiles also show a pronounced dip in the gallium concentration within the emitter. It is shown that the electric field created during the emitter diffusion could be the cause of such a dip, and the dip position, predicted on such a model, is close to that found experimentally. Similar effects produced by the diffusion of arsenic emitters are compared with these new observations on the effects of phosphorus emitter diffusions.