In electrical installations, as you know, power semiconductor devices—industrial diodes—are of great use. These are zener diodes, Zener diodes and the guest of our article -
What is a Schottky diode (named after the German physicist Walter Schottky), I can say briefly - it differs from other diodes in the operating principle based on a metal-semiconductor rectifying contact. This effect can occur in two cases: for an n-type diode - if the work function of the semiconductor is less than that of the metal, for a p-type diode - if the work function of the semiconductor is greater than that of the metal. The most popular are n-type Schottky diodes due to the high mobility of electrons, comparable to the mobility of holes.
Fig 1. Sectional view of a Schottky diode
For comparison, we take a bipolar diode. As they say: straight into the fire, let’s start with the shortcoming, and I think it’s the most important. Schottky diodes have a huge reverse current.
That's all with the minuses, now the good things are the pluses.
A huge number of Schottky diodes are manufactured using planar technology with an epitaxial n-layer, on the surface of which an oxide layer is created, in which windows are formed to form a barrier. The following metals are used as the latter: molybdenum, titanium, platinum, nickel. A ring of p-type silicon is formed over the entire area of the contact area ( Figure 2 a), which will serve to reduce the edge leakage currents. 
Fig 2 a., b.
The “guard” ring works in this way: the degree of doping and the dimensions of the p-region are designed in such a way that during overvoltages on the device, the breakdown current flows through the p-n junction, and not through the Schottky contact.
Here we see that p-type regions are formed directly in the active region of the Schottky transition. Since this design has two types of junction - a metal-silicon junction and a p-n junction - it occupies an intermediate position in its properties and characteristics. Thanks to the Schottky junction, it has minimal leakage currents, and due to the presence of the p-n junction, it has high voltages at forward bias.
Also the design shown in Figure 2 b
, has increased resistance to static electricity discharge. This follows from the principle of operation, which is that bulk leakage currents are closed in the depletion region of the p-n junction, thereby reducing the electric field at the metal-semiconductor interface under forward bias; the regions of spatial p-n junctions have a minimum width , and current-voltage characteristic (VAC) Fig.3
diode is close to the current-voltage characteristic of a typical diode design. With reverse voltages, the depletion region of the p-n junction increases as the applied voltage increases and the SCR of neighboring p-n junctions closes, forming a kind of “screen” that protects the contact Me-Si high voltages, which can cause large volumetric leakage currents. 
Fig. 3 Current-voltage characteristic of a Schottky diode
The current-voltage characteristic of a forward-biased Schottky diode is determined by the formula
which in shape coincides with the current-voltage characteristic of the pn-junction, but the current J 0 much higher than J s (typical values of a Schottky diode Al-Si at 25 WITH J 0 = 1.6 * 10 -5 A/cm 2, and for p- n-junction at N d = N a =10 16 A/cm 3, J s =10 -10 A/cm 2 )
When a Schottky diode is forward biased, the voltage across the semiconductor itself is added to the forward voltage drop across the junction. The resistance of this region contains two components: the resistance of the lightly doped epitaxial film (n -) and the resistance of the heavily doped substrate (n +). For a Schottky diode with low voltage tolerance (less than 40 V), these two resistances are of the same order of magnitude, since the n + region is much longer than the (n -) region (approximately 500 and 5 μm, respectively). The total resistance of silicon with an area of 1 cm2 is in this case from 0.5 to 1 mOhm, creating a voltage drop in the semiconductor from 50 to 100 mV at a current of 100A.
If a Schottky diode is designed to allow a reverse voltage greater than 40 V, the resistance of the lightly doped region increases very quickly, since a longer lightly doped region and an even lower carrier concentration are required to produce a higher voltage. As a result, both factors lead to an increase in the resistance (n -) of the diode region.
The high resistance is one of the reasons that conventional silicon Schottky diodes are not designed for voltages above 200 V.
To reduce reverse leakage currents and increase resistance to static electricity discharges, various techniques are used.
Thus, to reduce leakage currents and the yield of suitable Schottky diodes, a 0.05 μm depression is made in the window under the barrier layer, and after the formation of the depression in the epitaxial layer, annealing is carried out at a temperature of 650 degrees. In a nitrogen environment for 2-6 hours.
Reducing the reverse currents of molybdenum Schottky diodes is achieved by creating a getter layer before applying the epitaxial layer by polishing the back side of the substrate with a free abrasive, and after metallization of the Schottky electrode, the getter layer is removed.
By maintaining optimal ratios between the width and depth of the guard ring, it is also possible to significantly reduce reverse leakage currents and increase resistance to static.
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A Schottky diode is a semiconductor device (diode) realized through a metal-semiconductor contact. It received its name in honor of the German physicist Walter Schottky.
Features of Schottky diodes
In 1938, scientists created the basis for the theory of these semiconductor devices. Instead of a pn junction in such diodes, a metal semiconductor is used as a barrier. The region of the semiconductor material is united by the majority carriers. At the point of contact, a charge region of ionized acceptors begins to form. As a result, a potential barrier arises in the transition area, which is called the Schottky barrier. A change in its level leads to a change in the value of the current flowing through the Schottky diode. The main feature of such semiconductor devices is considered to be a low level of forward voltage reduction after the p-n junction, as well as the absence of a reverse recovery charge level.
Schottky diodes operate in the temperature range from minus 65 0 to plus 160 0 Celsius, the value of the permissible reverse voltage of industrially produced diodes is limited to 250 V. However, these devices are widely used in industrial electronics in low-voltage circuits, the reverse voltage of which is limited to tens of volts . The Schottky diode allows you to obtain the required value of the potential barrier by selecting the desired metal. A sufficiently low level of high-frequency noise allows the use of such diodes in switching power supplies, in digital equipment, as radiation receivers, light modulators, and in transformer blocks of analog equipment. They have found wide application in the design of solar panels. The Schottky barrier principle is used in the design and manufacture of high-speed microwave diodes. The Schottky diode is constructed in glass, plastic and metal housings. These devices are also available in SMD housings.
Advantages and disadvantages
Their advantage, unlike silicon diodes, is a fairly low voltage drop (up to 0.2-0.4 volts). Such a low drop value is typical exclusively for Schottky diodes. The Schottky barrier also has a lower electrical capacitance of the junction, which makes it possible to significantly increase the operating frequency of the device. These devices are also characterized by a reduced level of interference. The Schottky diode also has a number of disadvantages. The main thing is the high sensitivity to short-term surges in reverse current and voltage, which results in a short circuit and the diode burns out. Also, diodes of this type are characterized by an increase in the reverse current value with increasing crystal temperature.
Based on power, these semiconductor devices can be divided into three groups: low-power (their passing current does not exceed 3-5 amperes), medium-power (up to 10 amperes) and high-power (current reaches 60 amperes). Powerful Schottky diodes are used to operate in devices used to rectify alternating current. They provide the passage of direct current reaching tens of amperes. In this case, the voltage drop across the diode is only 0.5-1 V. The permissible value of the reverse voltage in Schottky diodes is 200-500 V.
Or in various electrical circuit diagrams there is such a thing as a Schottky diode. First of all, this is a special semiconductor diode, which has a small voltage drop when connected directly and consists of a semiconductor and metal. It got its name in honor of the German inventor Walter Schottky, who invented this electronic element.
In contact with
The permissible reverse voltage in an electronic component for industrial purposes is limited to 250 volts. On practice mainly used in low voltage circuits to prevent current flow in the opposite direction. Based on their power, they are divided into several groups: low-power, medium-power and high-power.
The device itself consists of a metal - semiconductor, glass passivation, a protective ring and metal. When an electric current begins to flow through the circuit, then on the protective ring and throughout the entire area of the semiconductor barrier will accumulate positive and negative charges, but in different parts of the body, in which an electric field will arise and heat will be generated, which is a big plus for some experiments in physics.
This electronic element differs from others in that it uses metal as a barrier - a semiconductor, which has one-way electrical conductivity and has many other distinctive properties. Such semiconductor metals can be gallium arsenide, gold, silicon carbide, tungsten, germanium, palladium, platinum, and so on.
The entire operation of the Schottky electronic element will depend on the selected metal. Silicon is especially often used because it is more reliable than others and works well at high power. Also more often than other metals They use a semiconductor based on gallium arsenide (GaAs) - a chemical compound of arsenic and gallium, less often - based on germanium (Ge). The manufacturing technology of these electronic elements is very simple, which is why it is the cheapest.
Also, the Schottky diode differs from others in its stable operation when current is supplied. For stability, special crystals are introduced into the body of this electronic element, which is a very delicate job, because negligence or inattention can lead to malfunction of the device. People rarely do this; most often this work is performed by a special robot - an automatic machine programmed for such an operation.
Like all electronic parts and elements have designations, on circuit diagrams this electronic element is depicted like this (see Fig. 1), which is somewhat different from the designation of a conventional semiconductor.
In the diagrams you can also see an image of a dual Schottky diode (see Fig. 2). These are two mounted electronic elements in one common building. Their anodes or cathodes are soldered, so they have three terminals.
This electronic element, like most, is marked on the side. And if the letters and numbers on the designation are not clear, then you can look at their decoding in the radio engineering reference book.
This device has its positive sides and its disadvantages.
Big minus The problem is that the reverse current can be very large. In some cases, for example, exceeding the required reverse current level even for a few amperes, the electronic element simply breaks down or fails at the most inopportune moment, regardless of whether it is new or old. Diode leaks can also often be observed, which can in some cases lead to dire consequences if semiconductor testing is neglected.
These electronic elements, presented above, can be found in our world almost everywhere: in computers, stabilizers, household appliances, radio broadcasting, television, power supplies, solar panels, transistors and in many other devices from all spheres of life.
In all cases, increases efficiency and performance, reduces the number of losses voltage dynamics, restores the reverse resistance of the current, absorbs the radiation of alpha, beta and gamma charges, allows you to work for quite a long time without breakdowns, keeps the current in the voltage of the electrical circuit.
You can diagnose the Schottky electronic element if the need arises, but this will take a little time. First of all, you need to unsolder one element from the diode bridge or electronic circuit. Inspect visually and check with a tester. As a result of these simple technical operations, you will find out whether the semiconductor is working or not. Although it is not necessary to desolder the entire assembly, because this is extra work, and most importantly - s waste of time.
You can also check this diode or diode bridge with a multimeter, but keep in mind that the manufacturer writes the current on the side of the device. We turn on the multimeter and bring its probes to the ends of the anode and cathode, and it will show us the voltage of the diode.
Sometimes it happens that a Schottky diode may become faulty due to some reasons. Let's look at them:
Moreover, in both cases you will not feel the smell of burning and you will not see smoke, since the housing has built-in special protection against such incidents. If suddenly in one transistor the above diode burned out, then make sure that this is the only device where you found a fault, because diodes definitely need to be checked.
Although sometimes there may not be such an opportunity to check the diodes for serviceability when necessary. Sometimes it happens like this that the computer starts to slow down, takes a very long time to turn on, and freezes. Perhaps the problem is related specifically to the diodes, and anyone can disassemble the processor and see what happened inside.
First of all, you need to turn off the power to the computer and open the power supply in the system unit. You can immediately notice the diodes. Check if there are holes or breaks in them. If there are, then you need to get them out and replace them with a new semiconductor, fixing the problems yourself, but it is better to seek help from professionals.
Schottky diodes have gained wide popularity and distribution in all areas of modern life, especially in electronics. They can be found as dual rectifier diodes, where two semiconductors are installed in one package and the ends of the anodes or cathodes are connected to each other, and simple ones, also happen to be very small (for example, very often found in small electrical parts).
This semiconductor is very often used in switching power supplies in household appliances, which significantly reduces losses and improves thermal operation. Also data electronic elements used in transistors as current rectifiers, and in such special diodes that are used to combine parallel power supplies.
Today the topic of our review is the Schottky diode. The topic is educational and printed specifically for beginner radio amateurs. In modern radio circuits, the term “Schottky Diode” is very common, so let’s find out what it is. A Schottky diode is a semiconductor diode made on the basis of a metal-semiconductor contact. Named after Walter Schottky. The schematic diagram of a Schottky diode is similar to a conventional diode with some minor differences.
Instead of a n-junction, Schottky diodes use a metal semiconductor as a barrier; in the region of this junction, a potential barrier arises - a Schottky barrier, a change in the height of which leads to a change in the flow of current through the device. The most important feature of Schottky diodes is the low forward voltage drop after the transition and the absence of reverse recovery charge. Based on the Schottky barrier, in particular, high-speed and ultra-fast diodes are made; they serve mainly as microwave diodes for various purposes.
Diode structure: 1 - semiconductor substrate; 2 - epitaxial film; 3 - metal-semiconductor contact; 4 - metal film; 5 - external contact.
Such a diode allows you to obtain the desired height of the potential barrier, by choosing the right metal, a very low level of high-frequency noise, which makes it possible to use the Schottky diode in switching power supplies and in digital equipment. Schottky diodes are also used as radiation receivers, light modulators, and are widely used in solar batteries. Among the disadvantages of these types of diode, it is worth noting the sensitivity to reverse current and voltage values, due to which the diode can overheat and fail.
Operates in a temperature range from -65 to plus 160 degrees Celsius, the permissible reverse voltage of industrial Schottky diodes is limited to 250 volts. Such a part has become an indispensable semiconductor device today. Schottky diodes are also available in SMD packages. Most often they are found in glass, plastic and metal cases. Author - AKA.
A Schottky diode differs from the fact that instead of a p-n junction, a metal semiconductor is used as a barrier. The potential barrier that arises in the region of this transition is called the Schottky barrier. If you change the height of the Schottky barrier, this will lead to a change in the flow of current through this device. Feature of this diode is that it has a low forward voltage drop after the transition, as well as no reverse recovery charge. To put it simply, using the Schottky barrier as a basis, they produce ultra-fast and high-speed diodes that serve as microwave diodes and have various purposes.
These are all advantages, but there are also disadvantages. Since these devices are highly sensitive to reverse voltage and current values, they often fail. The permissible reverse voltage of these diodes is limited to 250 V. The operating temperature of these devices varies from -65 to +160 degrees. Celsius. These diodes are also available in SMD packages in glass, plastic and metal versions.
