CIE Instructors' Corner - Theelectron.net

March 2010

Pros and Silicons
Q.	I have read in my lessons that silicon and germanium can be used to make transistors. But as I have read further, it seems that most transistors and other solid-state devices like SCRs are made of silicon. Why is this so?
A.	Silicon has several advantages over germanium. First, it is less expensive to make. Second, PN junctions made with silicon have much lower reverse leakage currents than those made with germanium. Thus, silicon transistors have much lower leakage and much better temperature sensitivity than do germanium transistors. This is one reason why we chose the germanium transistor in our transistor lab lessons for the temperature stabilization experiments. A third advantage of silicon transistors is that their maximum operating temperature is about 200° C. For germanium, this figure is 100° C. This is very important with power transistors, which must withstand higher operating tempuratures. A fourth advantage of silicon is that the technology for making highly pure crystalline silicon and turning it into a variety of electronic devices is very advanced.