The design and fabrication of a VHF medium-power transistor

This paper describes the design criteria of a diffused base mesa transistor capable of power output of 15 watts at 100 mc and 5 watts at 200 mc. Efficiencies of approximately 75% have been achieved as a 100 mc oscillator. Recent developments in the area of improving the reproductibility of the diffusion of impurities into silicon are reviewed. A method involving a "sealed box" for boron diffusion is outlined and the results of its use explained. Techniques concerning the application of high conductance metal layers to the base and emitter areas are described. Aluminum thicknesses of approximately 70,000 angstroms have been achieved by evaporation. Alternate methods of providing contact layers are discussed.