An 85-watt dissipation silicon power transistor

Production prototype silicon transistors have been made using large area diffused base structure. Simultaneous diffusion of gallium and phosphorus is used to form the diffused base structures. The geometry and doping level of the structure can be controlled by varying the impurity source composition and temperature, The phosphorus surface concentration is a much less rapidly varying function of source temperature than is the gallium surface concentration and is determined primarily by the source composition. Two line base contacts and one line emitter contact are attached to the wafer in a one-shot process in which all contacts are made simultaneously. The structure is then encapsulated in a hermetically sealed package. The electrical characteristics of a group of units are given. The transistors are capable of dissipating 85 watts at a 25°C mounting base temperature and have been used, as is described, in circuits to deliver 25 watts in Class A and 80 watts in Class B push-pull operation.