Germanium diodes, while rarely used today, used to be very common. Before the silicon diode, which is widely seen today, germanium diodes and vacuum tubes provided the only possibilities. In fact, the invention of the modern diode used germanium as the doped semiconductor.
Why are silicon diodes more widely used today? Silicon is not only cheaper than germanium, but it also has better manufacturing characteristics. Beyond this, silicon diodes don't suffer from some of the same problems with temperature affecting the diode's function. And lastly, silicon diodes, unlike germanium diodes, suffer from little reverse leakage current. However, these facts do not mean that the germanium diode has become extinct.
The uses of germanium diodes today vary. Most often, they are used in low-power applications that require a small voltage drop: germanium diodes only drop about 0.3 volts, while silicon diodes drop about 0.7 volts. With low-level logic systems, germanium diodes can provide a more efficient and stable system design.
These diodes are also used in crystal radio applications, because the low voltage required in the crystal (diode) allows the user to hear a louder signal. On a broader scale, the germanium diode is useful in general signal detection applications because of its efficiency.
Tune in next week for some testing of the germanium diode!
40 Uses for Germanium Diodes. New York: Sylvania Electric Products, n.d. Electron Tube Data Sheets. Web. 13 Nov. 2015. http://frank.pocnet.net/other/Sylvania/40_Uses_for_Germanium_Diodes.pdf
Sandoval, David. "Characteristics of Silicon & Germanium Diodes." EHow. Demand Media, n.d. Web. 13 Nov. 2015. http://www.ehow.com/list_6823105_characteristics-silicon-germanium-diodes.html
Seidenberg, Philip. "Archives:From Germanium to Silicon, A History of Change in the Technology of the Semiconductors." Engineering and Technology History Wiki. N.p., 25 July 2014. Web. 13 Nov. 2015. http://ethw.org/Archives:From_Germanium_to_Silicon,_A_History_of_Change_in_the_Technology_of_the_Semiconductors
"Semiconductor Tutorials- Germanium Diodes." American Micro Semiconductor. American Micro Semiconductor, n.d. Web. 13 Nov. 2015. http://www.americanmicrosemi.com/information/tutorial/index.php?t_id=7