A new higher ambient transistor

Interest in high speed transistor switching circuits whose operation is unaffected by large changes in ambient temperature led to an investigation of silicon-germanium alloy point-contact transistors because of the larger forbidden energy gap of silicon-germanium alloys. In germanium transistors, as far as temperature stability is concerned, Ic0is particularly poor. Ic0is the value of collector current, at a given collector voltage, with no emitter current. The Ic0of germanium units tested rose rather linearly from 20°C. to about 65°C., with a gradient of 25 µa/°C. but then entered a region of run away. A number of point-contact transistors have been manufactured using 3 per cent silion-germanium (10 ohm-cm, n-type), and the parameters r11, r12, r22, α, fc0and Ic0at room temperature, and values of Ic0as a function of temperature have been measured. Results show that 3 per cent silicon-germanium transistors are as good as germanium transistors in all respects and better in temperature stability. The values of Ic0for silicon-germanium transistors rose linearly from 18° to about 95°C., with a gradient comparable to that of the germanium units below 65°C.