Abstract Silicon bipolar transistors have been made by substituting a shallow phosphorus implanation for the standard emitter deposition used in the manufacture of linear integrated circuits. The implantation was followed by a high temperature heat treatment (drive-in), which caused the implanted ions to diffuse deeper into the semiconductor to give emitter/base junction depths of typically 1.8 μm. When the high temperature heat treatment was performed in an oxidising atmosphere, the resulting transistors had lower gains and higher emitter/base leakages than the comparable standard diffused transistors. However, if an 1180°C drive-in, in an inert atmosphere, was performed prior to the oxidation drive-in, high gains and low emitter/base leakages were obtained. Alternatively, if the oxidation drive-in was omitted, and instead an inert drive-in performed at any temperature between 1000 and 1180°C, high gains and low emitter/base leakages were again obtained. Etching and TEM studies revealed that the low gains and high emitter/base leakages were again obtained. Etching and TEM studies revealed that the low gains and high emitter/base leakages were caused by emitter edge dislocations intersection the emitter/base junction around the perimeter of the emitter. A mechanism is suggested to describe the formation of the emitter edge dislocations.