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

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!