Silicon crystals have less free electrons than germanium crystals. However, silicon crystals can not easily be damaged by excessive heat. Peak inverse voltage ratings of silicon diodes are larger than germanium diodes. Si is less expensive due to the larger amount of elements.
Why is silicon preferred over germanium?
The back current in a Si diode is in the range of nanoamps. The same return current is in the microampere range for a Ge-based diode. While high power applications are taken into account, Si-based devices can tolerate high power (more than 50W) while Ge can only survive applications below 10W.
Germanium has a blocking voltage of only 50-70 V, while Si can withstand up to 100 V. Silicon is relatively easy and inexpensive to procure and process, while germanium is a rare material.
The temperature stability of silicon is good, it can withstand in the temperature range of typically 140 ° C to 180 ° C, while germanium is temperature sensitive only up to 70 ° C. Low voltage signal level. It loses only 0.2 V across the intersection.
It can easily be damaged by excessive voltage or current and can not handle power well.
What are the advantages of silicon over germanium?
Cost-effective: Silicon is relatively easy and inexpensive to procure and process, while germanium is a rare material that is typically found in copper, lead or silver deposits.
Due to its rarity, working with germanium is more expensive, making it harder (and sometimes more expensive) to find germanium diodes than silicon diodes.
Low reverse leakage current: The reverse current in the silicon flows in the order of the nanoamperes with respect to the germanium in which the reverse current is in the order of microamperes, thus the non-conduction accuracy of the diode Ge in inverse polarization decreases.
While the diode Si retains its property to a greater extent, that is, it allows a negligible amount of current to pass.
High reverse breakdown voltage: The Si diode has a significant reverse breakdown voltage of about 70 to 100 V with respect to Ge which has a reverse breakdown voltage of about 50 V.
Good temperature stability: The temperature stability of the silicon is good, it can withstand a temperature range typically from 140 ° C to 180 ° C, while the germanium is sensitive to temperature only up to 70 ° C.
Large forward current: Silicon is much better for high current applications because it has a very high forward current in a range of ten amps, while germanium diodes have a very low on-state current in a range of microamps.
Why is silicon usually preferred to germanium in the manufacture of semiconductor devices?
Silicon is abundant on the earth’s surface and therefore cheaper than germanium. The PIV (Peak Inverse Voltage) rating of silicon is much higher than germanium and therefore can withstand much higher temperatures than germanium.
The PIV rating determines how much resistance a diode can make before breakthrough V (s) The forbidden energy band of silicon is 1.1ev and thus higher than that of germanium (0.66ev), which makes silicon more stable and reduces the leakage current.
The corresponding equation is [I = I (0) e ^ (v / nv (t) – 1)]
Silicon can easily react with oxygen and produces SiO2, which is used as a perfect insulator in the semiconductor industry as a dielectric and in IC fabrication processes such as diffusion and ion implantation.
The variation of collector turn-off current with temperature is lower in silicon compared to germanium.