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Difference between Silicon Diode and Germanium Diode
A diode is a two-terminal semiconductor device which allows electric current to flow in only one direction, and blocks the current flow in the reverse direction. Diode is normally made up of semiconductor materials like silicon or germanium.
Based on construction and operation, there are several types of semiconductor diodes, but the most common type of semiconductor diode is the pn-junction diode. A pn-junction diode is formed by fusing a p-type semiconductor with an n-type semiconductor, where p-type semiconductor acts as the anode terminal and the n-type semiconductor acts as the cathode of the diode.
When a forward voltage is applied to the diode, it allows the flow of current through it. When the reverse biased voltage is applied, then the diode blocks the flow of current through it.
Diodes are widely used in a variety of electronic circuits like rectifiers, modulators, battery chargers, voltage regulators, voltage multipliers, and more.
Based on the semiconductor material used for manufacturing, diodes are classified in two types namely, Silicon Diode and Germanium Diode. Silicon and germanium diodes are different from each other in terms of their electrical properties, performance, and uses.
Read this article to learn more about Silicon and Germanium Diodes and how they are different from each other.
What is a Silicon Diode?
When the silicon semiconductor material is used for fabricating a semiconductor diode, then it is called a silicon diode. A silicon diode is constructed by join a p-type silicon material with an n-type silicon material. Due to the superior electrical properties and performance of silicon material, the silicon diodes are more commonly used in electronic circuits and devices than germanium diodes.
Silicon diodes provide high operating temperature range and high forward voltage drop, making them suitable for rectification, signal modulation, and voltage regulation applications. For a silicon diode, the forward voltage drop is typically around 0.7 volts. They also have better reverse recovery characteristics than germanium diodes. Due to high operating temperature range, the silicon diodes provide a stable operation in high temperature conditions.
What is a Germanium Diode?
A semiconductor diode fabricated from germanium semiconductor material is called a germanium diode. Similar to the silicon diode, a germanium diode is formed by joining a p-type germanium material with an n-type germanium material.
Germanium diodes have a lower forward voltage drop than silicon diodes. It is typically around 0.3 volts. Hence, germanium diodes are better suited for low voltage applications.
For a germanium diode, the reverse leakage current is higher than that of a silicon diode. Hence, these are not suitable to operate in high temperature conditions. However, the germanium diodes have a higher signal amplification coefficient, which makes them better suited for signal amplification in small-signal amplifiers.
Germanium diodes are not much used, but they are used in some special applications where lower forward voltage drop and higher temperature sensitivity is desired such as in photodiodes, light sensing applications, etc.
Difference between Silicon Diode and Germanium Diode
The following table highlights all the significant differences between silicon diode and germanium diode −
Parameter |
Silicon Diode |
Germanium Diode |
|---|---|---|
| Basic | A diode which is formed from silicon semiconductor material is called a silicon diode. |
A diode which is formed from germanium semiconductor material is called a germanium diode. |
| Forward voltage drop/ Threshold voltage | Silicon diode has a forward voltage drop of around 0.7 volts. |
Germanium diode has a forward voltage of around 0.3 volts. |
| Reverse leakage current | Silicon diode has a reverse leakage current of the order of nano ampere (nA). |
Germanium diode has a reverse leakage current of the order of milli-ampere (mA). |
| Temperature stability | Silicon diodes have a stabile operation at higher temperatures, typically up to 200 °C. |
Germanium diodes a relatively lower temperature stability, typically up to 85 °C. |
| Peak Inverse Voltage (PIV) | Silicon diodes have a higher peak inverse voltage. |
The peak inverse voltage of a germanium diode is lower than that of a silicon diode. |
| Operating temperature range | Silicon diodes operate reliably up to 170 °C temperature. |
Germanium diodes have a lower operating temperature range, they operate reliably up to 100 °C. |
| Switching speed | Silicon diodes have higher switching speeds. |
Germanium diodes have lower switching speeds. |
| Signal amplification factor | Silicon diodes have a smaller signal amplification factor. |
The signal amplification factor for germanium diodes is higher. |
| Reverse recovery time | The reverse recovery time for silicon diodes is shorter. |
Germanium diodes have a longer reverse recovery time. |
| Cost | Silicon diodes are cheaper. |
Germanium diodes are expensive. |
| Noise | Silicon diodes are less affect by the electronic noise. |
Germanium diodes are more easily affected by electronic noise. |
| Reverse saturation current | Silicon diodes have lower reverse saturation current, typically 1 nA. |
Germanium diodes have higher reverse saturation current, typically 1000 nA. |
| Applications | Silicon diodes are used in a range of applications like rectification, modulation, voltage regulation, voltage multiplication, etc. |
Germanium diodes are used in some niche applications like small signal amplification, light sensing applications, and photodiodes, etc. |
Conclusion
Both silicon and germanium diodes are commonly used in different electronic circuits and devices. Silicon and germanium diodes have many similarities like unidirectional current flow, etc. but they are absolutely different from each other as described in the above table.
The most significant difference between a silicon diode and a germanium diode is that silicon diodes have higher threshold voltage (typically 0.7 volts) and high thermal stability, whereas germanium diodes have lower threshold voltage (typically 0.3 volts) and lower thermal stability. Therefore, silicon diodes are suitable for high voltage and high temperature applications, while germanium diodes are suitable for low voltage and low temperature applications. Overall, the selection between silicon diode and germanium diode depends on requirements of the electronic circuits and applications.
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