What is Schottky Diode?
A Schottky diode, widely popular as barrier diode, refers to a metal-semiconductor diode that comprises lower voltage drops than usual PN-junction diodes. On top of that, it possesses a fast switching speed.
Their advantage includes the fact that their forward voltage drop is significantly lower than PN-junction diodes. It is because they constitute a metal electrode that links with N-type semiconductor. Contrarily, a PN-junction diode comprises P-type material and N-type material.
In this case, a P-type semiconductor refers to an intrinsic or pure semiconductor, such as silicon or germanium. In this case, one has to add a trivalent impurity. These trivalent impurities include Boron (B), Gallium (Ga), Indium (In), and Aluminum (Al). These are also acceptor impurities.
On the other hand, N-type materials refer to the integration of phosphorus, arsenic, antimony, and bismuth to pure semiconductors.
How Does a Schottky Diode Function?
A diode in this category functions as per the Schottky diode theory. It states that an essential factor in its functioning is fast switching rate and considerably lower voltage drop.
Also, it lacks the propensity to store electrical charges at their diode junctions. One of the reasons that enable its working is the overall lack of a depletion layer. In most cases, when current passes through a diode, the terminals witness a drop in voltage.
The drop conventionally ranges between 0.15 and 0.45 volts as opposed to an ordinary PN-junction diode. In the case of the latter, the spectrum of voltage drop is 0.6 to 1.7 volts. It happens mainly because current advances in a forward direction
Schottky diode working leverages the low voltage drop to generate a higher efficiency and output. For this to happen, the N-type semiconductor has to function as a cathode. The metal assumes the role of an anode.
What is Schottky Diode Symbol?
The following diagram represents the Schottky diode symbol –
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In the above diagram, the anode section is essentially a metal, such as molybdenum, chromium, tungsten, or platinum. On the other hand, n-type semiconductors such as the integration of silicon and bismuth stand for the cathode section.
What is Schottky Diode Construction?
The following figure is a pictorial representation of Schottky diode construction and working –
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In this figure, you can see that a lightly doped n-type semiconductor connects to a metal electrode or the anode. Here, you can refer to the connection as ‘metal-semiconductor junction’. When current flows in a forward direction, electrons travel from the n-type material end to the metal anode.
The drift of majority charge carriers heavily influences the overall current component passing through this category of a diode. However, such diodes also exhibit the properties of a rectifying diode.
The primary reason behind this is that diode conduction ceases and blocks the flow of current. It is due to the absence of p-type semiconductor. As a result, these diodes respond rapidly to reverse bias alterations.
What are the Characteristics of a Schottky Diode?
Since you know what is Schottky diode and its construction, it is time to move on to its characteristics.
Therefore, Schottky diode characteristics are as follows –
When compared with conventional PN-junction diodes, these diodes exhibit significantly lower drops in forward voltage.
Forward voltage drops vary between 0.15 and 0.45 volts, as opposed to 0.6 to 1.7 volts in PN-junction diodes.
Forward drop in these diodes increases with the enhancement of doping concentration of N-type semiconductors.
The drop in forward voltage in a Schottky barrier constitutes semiconductors such as Silicon.
Besides, these also act as a unipolar device owing to the lack of current flow from metals to N-type conductors.
The implemented metals do not undergo charge storage. As a result, these switch considerably quickly with a minimum noise component.
Furthermore, Schottky diode applications include the following –
Implementation in the electronics industry due to its properties as a general diode rectifier.
Radio Frequency (RF) applications also find broad uses of this technology.
These also find application in signal detection and logic circuits.
What are the Disadvantages of a Schottky Diode?
Despite its various uses,there are a few disadvantages of Schottky diodes. This includes –
High reverse current.
Susceptibility to leakages due to metal-semiconductor junction.
These cannot withstand significant reverse voltage.
Since you are now aware of what is Schottky diode, you should check out related concepts to know a lot more about this subject. You can also download our Vedantu app to avail a convenient and interactive learning experience.
FAQs on Schottky Diode
1. What is a Schottky diode and what is its primary function in an electronic circuit?
A Schottky diode is a special type of semiconductor diode formed by a junction between a semiconductor (usually an n-type silicon) and a metal. Its primary function is to act as a very fast-switching device with a low forward voltage drop, typically around 0.2V to 0.3V, compared to the 0.6V to 0.7V of a standard silicon P-N diode.
2. How does the metal-semiconductor junction in a Schottky diode enable its fast switching speed?
The fast switching speed is due to its unique structure. Unlike a standard P-N diode that stores charge in its depletion region, a Schottky diode operates using majority carriers (electrons in n-type material). There is no minority carrier charge storage, so when the diode's bias is switched from forward to reverse, there's no delay required to clear out stored charges. This allows it to switch almost instantaneously, making it ideal for high-frequency applications.
3. What is the key difference between a Schottky diode and a conventional P-N junction diode?
The key difference lies in their junction, performance, and application. Here’s a quick comparison:
- Junction: A Schottky diode has a metal-semiconductor junction, while a standard diode has a P-type semiconductor to N-type semiconductor (P-N) junction.
- Forward Voltage Drop: Schottky diodes have a much lower forward voltage drop (approx. 0.2V) than P-N diodes (approx. 0.7V for silicon).
- Switching Speed: Schottky diodes are significantly faster due to the absence of minority carrier storage.
- Reverse Current: Schottky diodes typically exhibit a higher reverse leakage current than P-N diodes.
4. What are the most common real-world applications of a Schottky diode?
Due to their unique characteristics, Schottky diodes are used in many modern electronic systems. Common applications include:
- Switch-Mode Power Supplies (SMPS): Used as rectifiers because their high speed and low voltage drop improve efficiency.
- RF (Radio Frequency) Circuits: Employed as detectors and mixers in high-frequency applications.
- Voltage Clamping and Protection: To protect sensitive components from voltage spikes.
- Logic Gates: In Schottky TTL (Transistor-Transistor Logic) families to increase switching speed.
- Solar Panels: Used as bypass diodes to prevent current from flowing back into shaded cells, improving overall panel efficiency.
5. How do the V-I characteristics of a Schottky diode differ from a standard diode?
The V-I (Voltage-Current) characteristics of a Schottky diode are distinct. In forward bias, it begins to conduct at a much lower voltage (the 'knee' voltage is around 0.2-0.3V). In reverse bias, it shows a significantly higher reverse leakage current (I_R) compared to a P-N diode. Additionally, its reverse breakdown voltage is generally lower, making it less suitable for high-voltage rectification tasks.
6. What is the circuit symbol for a Schottky diode?
The circuit symbol for a Schottky diode is similar to that of a standard diode but with a distinct modification to the cathode bar. It consists of the standard triangle pointing towards a line, but the line is bent into an 'S' or 'Z' shape. This unique symbol helps engineers immediately identify it in a circuit diagram and distinguish it from a standard diode or a Zener diode.
7. Why would an engineer choose a Schottky diode over a Zener diode for a high-frequency application?
An engineer would choose a Schottky diode because their functions are fundamentally different. A Schottky diode is designed for fast forward-biased switching and rectification. In contrast, a Zener diode is designed to operate in reverse breakdown to provide a stable reference voltage. For a high-frequency switching power supply, the Schottky’s low forward voltage drop and fast recovery are essential for efficiency, while a Zener diode would be completely unsuitable for that role.
8. What is the main disadvantage of a Schottky diode and why does it occur?
The main disadvantage of a Schottky diode is its high reverse leakage current and relatively low reverse breakdown voltage. This occurs because the metal-semiconductor barrier is thinner and less robust than a P-N junction. This thin barrier allows some electrons to 'tunnel' through even under reverse bias, creating leakage. This characteristic limits its use in applications requiring very low leakage or tolerance for high reverse voltages.
