Injected carrier concentrations in diffused silicon transistors by observations of interband carrier recombination

Autoluminesence of diffused silicon transistors produced by intrinsic recombination radiation was used to observe injected carrier concentrations under various operating conditions. Current theories of device operation will be discussed in terms of these observations. Infrared photomicrographs of diffused silicon transistors of various geometries will be shown and used to examine the design adequacy for various operating conditions. The most striking feature of the carrier distributions is the negligible injected carrier density except at the emitter perimeter. This is a result of the reduction of the emitter forward bias under the central part of the emitter due to lateral flow of base current. The photomicrographs provide a spectacular confirmation of this aspect of existing design theory.