Why don't we use germanium as a control device in silicon control rectifier?

Answer 1

Generally SCR is used at high power applications, in order to withstand the temperature dissipated in the SCR, THERMAL STABILITY is very high enough. It means that thermal stability of silicon is very high compared to germanium that's why germanium is not preferred. But that does not mean it is not possible, in fact before silicon became common in the 1960s devices equivalent to the SCR were built using germanium!

Answer 2

Generally silicone controlled rectifiers are used at high power applications in order to withstand the temperature dissipated across the scr. Germanium is not preferred because its thermal stability is not very high.

Answer 3

Actually in the late 1950s and early 1960s when germanium was the dominate semiconductor, devices similar to the SCR were made with germanium. They were called thyristors, similar to the gas filled tube the thyratron. However as germanium can only operate up to junction temperatures of about 60C and silicon can operate up to junction temperatures of 150C, it is much easier to make high power SCRs than thyristors. Also germanium devices must be packaged in expensive hermetically sealed metal cans, silicon devices can be packaged in inexpensive plastic.