Light Emitting Diode Construction Advantages And Disadvantages

The most common source of light is the Light Emitting Diode or LED. There are many uses for LEDs, whether your car’s headlights or daytime running lights or your living room lights.

Like most legacy filament bulbs, LEDs and fluorescent bulbs require a special circuit to work. These are also known as LED Drivers or ballast for fluorescent bulbs.

LEDs will inevitably be part of our daily lives. This makes it a great idea for engineers, driver designers, and others interested in this topic. First, learn the basics of Light Emitting Diode. This article provides a quick overview of LED. It includes an introduction to the electric symbol, types, construction, characteristics, and LED Drivers.

[su_note note_color=”#9c8a0b”]NOTE: This article is also available in a simplified version LED-Light Emitting Diode”, which provides a simplified overview of LEDs without getting into technical details.[/su_note]

Introduction to light emitting diodes

These diodes are the most visible and emit a narrow bandwidth of visible light at different wavelengths, invisible light for remote controls, or laser-type light when forward current passes through them.

The “Light Emitting Diode,” or LED as commonly known, is a specialized diode with very similar electrical characteristics as a PN junction. An LED can pass current in its forward direction but will block current flowing in reverse.

Light-emitting diodes (LEDs) are made of a thin layer of semiconductor material that is very heavily doped. Depending on the material and doping, an LED can emit color at a specific wavelength when forward-biased.

Forward biased diodes allow electrons from the semiconductors conduction band to recombine and release enough energy to create photons that emit monochromatic (single-colored) light. In addition, this thin layer allows for a fair number of photons to leave the junction and radiate away, producing a colored light output.

Two of the most important semiconductor light emitting sources are LED and LASER diodes. LASER diodes operate on stimulated emission while LEDs work on spontaneous emission.

Light Emitting Diodes (LEDs) are the most popular source of light in electronic components. They are used to display the time and other data on certain displays. The Opto-semiconductor LEDs convert electric current into light. The area of an LED is typically very small, and it can have many integrated optical components to design its radiation pattern. Therefore, this LED has the advantage of being more cost-effective and lasts longer than the laser diode.

Two elements are the main components of a semiconductor that make up a light-emitting diode. These are P-type positively charged holes and N-type negatively charged electrons.

The positive P side of the diode connects to the power supply while the N side is connected to the ground. This is known as forwarding bias. It allows electric current to flow through it. The majority and minor charge carriers of the N side and P sides combine to neutralize the charge carriers at the PN junction.

In turn, electrons and holes migrate, which releases photons. This energy is in the form of monochromatic light at a constant wavelength, usually in nm. It is similar to the color of an LED. LED emission has a narrow color spectrum.

It can generally be described as a specific spectrum of electromagnetic wavelengths. Due to the nature and manufacturing of the semiconductor, the LED’s emission range of colors is limited. The most common colors for LED are amber, white, red, yellow, blue, amber, and yellow.
You can combine the light of red, green, and blue colors to create white light with limited brightness. The working voltage for red, green, and amber colors is approximately 1.8 volts. The breakdown voltage of the semiconductor materials used in the manufacture of LED can determine the actual working voltage. The PN junction of semiconductor materials is what determines the color of the LED light.

This is because of the different energy gap band structures of semiconductor materials. As a result, different numbers of photons are emitted at different frequencies. The wavelength of light depends upon the band gap between semiconductor materials at the junction. In addition, the intensity of light is dependent on the amount of energy applied to the diode. Compound semiconductors can maintain the output wavelength, so the required color can still be seen while keeping the output within the visible spectrum.

Electronic means can control light in many ways. For example, electroluminescence, a solid-state process, is used to produce light in light-emitting diodes. Solid-state procedures can produce coherent light under certain conditions, similar to laser diodes.

Construction of Light emitting diode

A Light Emitting Diode’s construction is quite different from a regular signal diode. An LED’s PN junction is protected from vibration and shock by a transparent, hard plastic epoxy resin hemispherical-shaped body.
Surprisingly, LED junctions do not emit much light. The epoxy resin body is designed so that photons of light emitted from the junction are reflected away by the substrate base to which it is attached. Instead, they are focused upwards through a domed top of the LED, which acts as a lens, concentrating the light. This is why the LED’s top appears brighter.

Not all LEDs have a dome-shaped epoxy shell. Indicator LEDs may have a rectangular- or cylindrical-shaped construction with a flat top surface, or their bodies are shaped into an arrow or bar. All LEDs have two legs that protrude from the bottom.

Nearly all modern light-emitting diodes ( -) have their cathode terminal, which is identified either by a notch on the body or by the cathode lead that is shorter than the other, as the anode (+ ) lead has a longer length than the cathode(k).

The light-emitting diode generates a “cold” generation of light, which is superior to traditional incandescent lamps or bulbs that produce large amounts of heat when they are illuminated. This results in higher efficiencies than normal “light bulbs” because most of the energy generated radiates outwardly within the visible spectrum. Solid-state LEDs can be very small and last longer than other light sources.

These LEDs were designed to maximize the recombination charge carriers on the surface of the PN junction.

[su_note note_color=”#9c8a0b”]

• The substrate doping concentration can be increased to allow the electrons of the minor charge carriers, which are the electrons that move up the structure, recombine, and emit light from the LED surface.
• You can increase the diffusion time of charge carriers by increasing L = Dt, where D is the coefficient for diffusion and t the charge carrier lifetime. If the critical value is exceeded, there may be re-absorption of the photons released into the device.[/su_note]

Forward bias connects the diode in a way that allows charge carriers to acquire enough energy to overcome the PN junction’s barrier potential. Forward bias can be applied to inject the minor charge carriers of P-type and N-type across the junction. They then recombine with majority carriers. Radiative or nonradiative, this recombination may occur between majority and minority charge carriers. Radiative recombination emits heat, while nonradiative recombination emits sunlight.

Organic Light-Emitting Diodes (OLED).

The organic light-emitting diodes are made from organic semiconductor materials. An organic semiconductor is an organic material electrically conductive in a part of the molecule or all of it due to the conjugated electron. It can be either in the crystal phase of polymeric molecules. It is a thin material with low cost and low voltage, which allows for high radiation patterns, high contrast, intensity, and maximum radiance.

Light Emitting Diode Colors

Contrary to normal semiconductor signal diodes, which are used to switch circuits, rectifiers, and power electronics circuits made of silicon or germanium semiconductor material, Light Emitting Diodes, which are made from compound semiconductor materials like Gallium Arsenide Phosphide and Silicon Carbide, are mixed in different proportions to create a distinctive wavelength.

Different semiconductor compounds emit different levels of visible light. Therefore, the wavelength and color of the light emitted by the LED depend on the semiconductor material used to make it.