New advances in semiconductor materials now offer further improvements for light-emitting diode (LED) technology, and make it a leading technology for roadside displays. A major breakthrough in LEDs has been made with the new semiconductor material AlInGaP (aluminium indium gallium phosphide). LEDs using this technology have lighting efficiencies equal to those of halogen light sources, so that they are suitable for situations where conventional LEDs cannot operate, such as high ambient light conditions. Such LEDs are already being used in large outdoor displays, such as traffic information panels on roads. AlInGaP is already established as the industry standard for applications to cars, such as centre high-mounted stop lamps and all kinds of interior lights. The latest version of the AlInGaP LED generates an efficiency of around 20lumen/W, compared with up to 2lumen/W for conventional LEDs. With variations of doping levels, green, yellow, orange, and red colours can be emitted. The article gives some details of the LED structure and technology, and discusses the formula for the LED chip temperature. It briefly outlines the results of extensive life tests for the LED, which show that it can stand harsh environmental conditions. It also has high reliability, low power consumption, and low heat output in use.
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