What Is a Diode?
Diodes are one of the most versatile electrical components available. They regulate current flow by letting it pass in certain directions but blocking it in others.
A diode is a junction of two semiconductor materials with special characteristics. The p-n junction creates an insulating layer that either facilitates or hinders the movement of electrons depending on the voltage applied to it.
Characteristics
The various types of diodes have specific characteristics which make them useful for particular purposes. These characteristics are described on a technical data sheet for each device. It is important for engineers and technicians to be able to read and understand this information.
In a standard diode, there are two semiconductor materials with different special properties that come together at the junction. One of these is called the p-type semiconductor material and it has positively charged holes. The other is called the n-type semiconductor material and it has negatively charged electrons.
When the two of these materials are viewed under an electric microscope, they will have areas where the holes and electrons are concentrated. The area where the holes and electrons are concentrated is referred to as the depletion region. This region acts as an insulator and does not allow current to flow between the p-side and n-side of the diode.
When a forward voltage is applied to the diode, it causes this depletion region near diode the p-n junction to narrow. This allows the holes and electrons to move closer to the junction. This then overcomes the electric field and current flows across the diode. When the diode is reverse biased, this reverse electric field widens and makes it extremely difficult for most charge carriers to cross.
Applications
A diode is used in a variety of electrical devices and circuits. Its main function is to allow electric current to flow in one direction while blocking the other, a process called rectification. A diode has two terminals, known as anode and cathode, with a voltage applied across it that controls the flow of current.
The most common type of diode is the p-n junction, which consists of two semiconductor materials fused together—one with more electrons (n-type) and the other with holes (depleted areas of electrons). When a positive voltage is applied to the n-side of the p-n junction, free electrons from the n-type side move into the p-side and fill the holes there, allowing current to flow.
When the voltage is applied in reverse, however, this enlarges the depletion region, creating an electric field that prevents most charge carriers from crossing the junction. This is why the arrow on the diode symbol points against the direction of normal current flow.
A Gunn diode, which is similar to a standard p-n diode, reduces the threshold voltage by using metal instead of silicon. This makes it easier for the diode to react quickly and reduces the amount of diffusion capacitance that slows down the diode. This makes it ideal for high-frequency applications up to GHz. This type of diode also works as a transient-voltage suppressor to divert voltage spikes away from other electronics.
Materials
Diodes are a vital safeguard for the current that powers many electronic devices, keeping them safe from damaging voltage reversals. This unidirectional flow is achieved through a fundamental structure within the device’s semiconductor materials.
To create a diode, silicon is doped with phosphorus, arsenic or antimony to add free electrons to the material. Boron, aluminum or gallium bind electrons to the silicon, creating excess positively charged holes. When these two different kinds of semiconductor material meet at the point of contact, the resulting depletion region forms a natural barrier preventing electrons from the n-side from combining with holes in the p-side. This keeps electric current from flowing until an external voltage is applied, pushing electrons and holes across the p-n junction.
The highest performance organic diode thus far has been built from pentacene and Au electrodes, achieving a rectifier frequency of 1.24 GHz. Although these are promising results, they still face several grand challenges to become commercially viable.
As the demand for high-frequency and DC power grows, researchers seek to develop new materials and fabrication methods for efficient diodes. Printed diodes are one example of this, utilizing organic semiconductors that are compatible with printing processes and offer low resistance at low voltages. However, their performance is limited by the materials’ inherent drawbacks. Matsusada Precision’s high-voltage and DC power supplies can help researchers test these materials to find the best solutions for their intended applications.
Design
Diodes are an extremely useful component that performs a variety of functions related to managing the direction of current flow. When correctly used, they protect our circuits from excessive current or sudden high-voltage bursts that could cause damage or fires.
This is because a diode acts as a sort of shield that redirects the excess energy away from our sensitive electronic parts that would otherwise be exposed to it. For example, it prevents our computer’s internal components from receiving dangerously high voltages originating from the power supply.
Whenever a reverse-biased diode receives a voltage, it Passive Component Supplier causes the depletion region to narrow near the junction between the P and N regions. This weakens the electric field within the depletion region, allowing most charge carriers (electrons in the N and holes in the P) to overcome the remaining electric fields to cross over to the other side of the junction.
A diode that is forward biased, on the other hand, will have the electrons and holes recombine in this area, so they would be unable to pass through. The current would stop flowing once the negative charges are recombined, and the voltage drop across the diode would be zero.