Silicon Vs Germanium Diode
The construction of a silicon diode starts with purified silicon. Each side of the diode is implanted with impurities (boron on the anode side, arsenic or phosphorus on the cathode side), and the joint where the impurities meet is called the “p-n junction.”
Silicon diodes have a forward-bias voltage of 0.7 Volts. Once the voltage differential between the anode and the cathode reaches 0.7 Volts, the diode will begin to conduct electrical current across its p-n junction. When the voltage differential drops to less than 0.7 Volts, the p-n junction will stop conducting electrical current, and the diode will cease to function as an electrical pathway.
Because silicon is relatively easy and inexpensive to obtain and process, silicon diodes are more prevalent than germanium diodes.
Germanium diodes are manufactured in a manner similar to silicon diodes. Germanium diodes also utilize a p-n junction and are implanted with the same impurities that silicon diodes are implanted with. Germanium diodes, however, have a forward-bias voltage of 0.3 Volts.
Germanium is a rare material that is typically found with copper, lead or silver deposits. Because of its rarity, germanium is more expensive to work with, thus making germanium diodes more difficult to find (and sometimes more expensive) than silicon diodes.