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Silicon
Yes, germanium was the only material used in transistors from when they were invented in 1947 until 1954 when the first successful silicon transistor was made. However the use of germanium still dominated transistors until the silicon mesa transistor was made commercially available by Fairchild Semiconductor in 1958. Development of the silicon planar transistor by Fairchild Semiconductor the next year ultimately made the integrated circuit possible. While almost all transistors today are silicon, there are still uses for germanium transistors so a few types are still made.
The primary reason that NPN transistors are used more often than PNP transistors is that they usually operate faster (at higher frequencies) because the mobility of the current carriers in NPN transistors (electrons) is much higher than that of the current carriers in PNP transistors (holes).
ICs contain lots of transistors, which are made up of P and N silicon.
For the same reason it is used in transistors and ICs: its a very good semiconductor. Note: equivalent devices have been made with germanium in the past, when most transistors were germanium. But they called them thyristors not GCRs.