High-frequency silicon alloy transistor

The silicon alloy transistor is a high-frequency, p-n-p type transistor capable of operation at high temperatures. Its temperature characteristic, derived principally from the use of silicon as the semiconductor, permits operation from - 70°C to 150°C. It achieves its high-frequency characteristic through accurate control of the base geometry. The n-type base of silicon is accurately machined by jet electrochemical techniques. Alloy contacts of aluminum are fused into the bottoms of the etch pits without producing appreciable change in base geometry. The depth of alloy is limited by the thickness of the aluminum, by the temperature, and by the length of time for alloying. Lead wires are soldered to the aluminum contacts and the transistor hermetically sealed in glass-metal containers. The electrical characteristics of typical silicon alloy transistors include an Icoof 0.005 µa, a common emitter forward current gain of 12, and an alpha-cutoff frequency of 12 mc.