Medium power high-speed germanium alloy transistors

A complementary pair of medium-power high-speed switching transistors was required to satisfy the needs of an electronic switching system. Units have been designed and produced which exhibit a median cutoff frequency of 7 mc and a punch-through voltage of 70 volts. High yields have been achieved on established production lines by very close manufacturing controls of the critical alloying variables, namely, germanium wafer thickness, alloyed junction area, concentricity, mass of alloying material, alloying temperature, and special material properties such as orientation and etch-pit density. A vacuum-tight transistor structure has been designed to permit the dissipation of one-half watt of power at 25°C in free air. The structure embodies an all-copper cold-welded encapsulation for efficient heat removal. Important techniques concerning the cold-welding process will be discussed, and the particular die contour used will be illustrated in some detail. Additional cleanliness advantages are obtained by use of the cold welded seal.