The earliest GaP and GaAsP homojunction red, yellow, and green low luminous efficiency LEDs in the 1970s have been applied to indicator lights, digital and text displays. From then on, LED began to enter various application fields, including aerospace, aircraft, automobiles, industrial applications, communications, consumer products, etc., covering various sectors of the national economy and thousands of households. By 1996, LED sales worldwide had reached billions of dollars. Although LEDs have been limited by color and luminous efficiency for many years, GaP and GaAsLEDs have been favored by users due to their long lifespan, high reliability, low operating current, compatibility with TTL and CMOS digital circuits, and many other advantages.
In the past decade, high brightness and full-color have been cutting-edge topics in the research of LED materials and device technology. Ultra high brightness (UHB) refers to LED with a luminous intensity of 100mcd or more, also known as Candela (cd) level LED. The development progress of high brightness A1GaInP and InGaNFED is very rapid, and has now reached a performance level that conventional materials GaA1As, GaAsP, and GaP cannot achieve. In 1991, Toshiba of Japan and HP of the United States developed InGaA1P620nm orange ultra-high brightness LED, and in 1992, InGaA1P590nm yellow ultra-high brightness LED was put into practical use. In the same year, Toshiba developed InGaA1P573nm yellow green ultra-high brightness LED with a normal light intensity of 2cd. In 1994, Japan’s Nichia Corporation developed InGaN450nm blue (green) ultra-high brightness LED. At this point, the three primary colors required for color display, red, green, blue, as well as orange and yellow LEDs, have all reached Candela level luminous intensity, achieving ultra-high brightness and full-color display, making outdoor full-color display of light-emitting tubes a reality. The development of LED in our country started in the 1970s, and the industry emerged in the 1980s. There are more than 100 enterprises nationwide, with 95% of manufacturers engaged in post packaging production, and almost all of the required chips are imported from abroad. Through several “Five Year Plans” for technological transformation, technological breakthroughs, introduction of advanced foreign equipment and some key technologies, China’s LED production technology has taken a step forward.

1、 Performance of ultra-high brightness LED:
Compared with GaAsP GaPLED, ultra-high brightness red A1GaAsLED has higher luminous efficiency, and the luminous efficiency of transparent low contrast (TS) A1GaAsLED (640nm) is close to 10lm/w, which is 10 times greater than that of red GaAsP GaPLED. The ultra-high brightness InGaAlPLED provides the same colors as GaAsP GaPLED, including: green yellow (560nm), light green yellow (570nm), yellow (585nm), light yellow (590nm), orange (605nm), and light red (625nm, deep red (640nm)). Comparing the luminous efficiency of transparent substrate A1GaInPLED with other LED structures and incandescent light sources, the luminous efficiency of InGaAlPLED absorbing substrate (AS) is 101m/w, and the luminous efficiency of transparent substrate (TS) is 201m/w, which is 10-20 times higher than that of GaAsP GaPLED in the wavelength range of 590-626nm; In the wavelength range of 560-570, it is 2-4 times higher than GaAsP GaPLED. The ultra-high brightness InGaNFED provides blue and green light, with a wavelength range of 450-480nm for blue, 500nm for blue-green, and 520nm for green; Its luminous efficiency is 3-151m/w. The current luminous efficiency of ultra-high brightness LEDs has surpassed that of incandescent lamps with filters, and can replace incandescent lamps with a power of less than 1 watt. Moreover, LED arrays can replace incandescent lamps with a power of less than 150 watts. For many applications, incandescent bulbs use filters to obtain red, orange, green, and blue colors, while using ultra-high brightness LEDs can achieve the same color. In recent years, ultra-high brightness LEDs made of AlGaInP and InGaN materials have combined multiple (red, blue, green) ultra-high brightness LED chips together, allowing for various colors without the need for filters. Including red, orange, yellow, green, and blue, their luminous efficiency has exceeded that of incandescent lamps and is close to that of forward fluorescent lamps. The luminous brightness has exceeded 1000mcd, which can meet the needs of outdoor all-weather and full-color display. The LED color large screen can represent the sky and ocean, and achieve 3D animation. The new generation of red, green, and blue ultra-high brightness LEDs has achieved unprecedented

2、 Application of ultra-high brightness LED:
Car signal indication: The car indicator lights on the outside of the car are mainly direction lights, taillights, and brake lights; The interior of the car mainly serves as lighting and display for various instruments. Ultra high brightness LED has many advantages compared to traditional incandescent lamps for automotive indicator lights, and has a wide market in the automotive industry. LEDs can withstand strong mechanical shocks and vibrations. The average working life MTBF of LED brake lights is several orders of magnitude higher than that of incandescent bulbs, far exceeding the working life of the car itself. Therefore, LED brake lights can be packaged as a whole without considering maintenance. Transparent substrate Al GaAs and AlInGaPLED have significantly higher luminous efficiency compared to incandescent bulbs with filters, allowing LED brake lights and turn signals to operate at lower driving currents, typically only 1/4 of incandescent bulbs, thereby reducing the distance that cars can travel. Lower electrical power can also reduce the volume and weight of the car’s internal wiring system, while also reducing the internal temperature rise of integrated LED signal lights, allowing the use of plastics with lower temperature resistance for lenses and housings. The response time of LED brake lights is 100ns, which is shorter than that of incandescent lights, leaving more reaction time for drivers and improving driving safety. The illumination and color of the external indicator lights of the car are clearly defined. Although the internal lighting display of cars is not controlled by relevant government departments like external signal lights, car manufacturers have requirements for the color and illumination of LEDs. GaPLED has long been used in cars, and ultra-high brightness AlGaInP and InGaNFED will replace more incandescent bulbs in cars due to their ability to meet the requirements of manufacturers in terms of color and illumination. From a price perspective, although LED lights are still relatively expensive compared to incandescent lights, there is no significant difference in price between the two systems as a whole. With the practical development of ultra-high brightness TSAlGaAs and AlGaInP LEDs, prices have been continuously decreasing in recent years, and the magnitude of the decrease will be even greater in the future.

Traffic signal indication: Using ultra-high brightness LEDs instead of incandescent lamps for traffic signal lights, warning lights, and sign lights has now spread all over the world, with a broad market and rapidly growing demand. According to statistics from the US Department of Transportation in 1994, there were 260000 intersections in the United States where traffic signals were installed, and each intersection must have at least 12 red, yellow, and blue-green traffic signals. Many intersections also have additional transition signs and pedestrian crossing warning lights for crossing the road. In this way, there can be 20 traffic lights at each intersection, and they must light up simultaneously. It can be inferred that there are approximately 135 million traffic lights in the United States. At present, the use of ultra-high brightness LEDs to replace traditional incandescent lamps has achieved significant results in reducing power loss. Japan consumes about 1 million kilowatts of electricity per year on traffic lights, and after replacing incandescent bulbs with ultra-high brightness LEDs, its electricity consumption is only 12% of the original.
The competent authorities of each country must establish corresponding regulations for traffic signal lights, specifying the color of the signal, minimum illumination intensity, spatial distribution pattern of the beam, and requirements for the installation environment. Although these requirements are based on incandescent bulbs, they are generally applicable to the currently used ultra-high brightness LED traffic signal lights. Compared with incandescent lamps, LED traffic lights have a longer working life, generally up to 10 years. Considering the impact of harsh outdoor environments, the expected lifespan should be reduced to 5-6 years. At present, ultra-high brightness AlGaInP red, orange, and yellow LEDs have been industrialized and are relatively inexpensive. If modules composed of red ultra-high brightness LEDs are used to replace traditional red incandescent traffic signal heads, the impact on safety caused by sudden failure of red incandescent lamps can be minimized. A typical LED traffic signal module consists of several sets of connected LED lights. Taking a 12 inch red LED traffic signal module as an example, in 3-9 sets of connected LED lights, the number of connected LED lights in each set is 70-75 (a total of 210-675 LED lights). When one LED light fails, it will only affect one set of signals, and the remaining sets will be reduced to 2/3 (67%) or 8/9 (89%) of the original, without causing the entire signal head to fail like incandescent lamps.
The main problem with LED traffic signal modules is that the manufacturing cost is still relatively high. Taking the 12 inch TS AlGaAs red LED traffic signal module as an example, it was first applied in 1994 at a cost of $350. By 1996, the 12 inch AlGaInP LED traffic signal module with better performance had a cost of $200.

It is expected that in the near future, the price of InGaN blue-green LED traffic signal modules will be comparable to AlGaInP. Although the cost of incandescent traffic signal heads is low, they consume a lot of electricity. The power consumption of a 12 inch diameter incandescent traffic signal head is 150W, and the power consumption of a traffic warning light crossing the road and sidewalk is 67W. According to calculations, the annual power consumption of incandescent signal lights at each intersection is 18133KWh, equivalent to an annual electricity bill of $1450; However, LED traffic signal modules are very energy-efficient, with each 8-12 inch red LED traffic signal module consuming 15W and 20W of electricity respectively. The LED signs at intersections can be displayed with arrow switches, with a power consumption of only 9W. According to calculations, each intersection can save 9916KWh of electricity per year, equivalent to saving $793 in electricity bills per year. Based on an average cost of $200 per LED traffic signal module, the red LED traffic signal module can recover its initial cost after 3 years using only the electricity saved, and begin to receive continuous economic returns. Therefore, currently using AlGaInLED traffic information modules, although the cost may seem high, is still cost-effective in the long run.